Chapter 17 MCQs

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

1

Which row gives electromagnetic waves in order of increasing frequency?

A gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, radio waves
B radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays
C radio waves, infrared, microwaves, visible light, ultraviolet, gamma rays, X-rays
D visible light, infrared, microwaves, radio waves, ultraviolet, X-rays, gamma rays

---

2

Which row gives electromagnetic waves in order of decreasing wavelength?

A gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, radio waves
B radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays
C radio waves, infrared, microwaves, visible light, X-rays, ultraviolet, gamma rays
D ultraviolet, X-rays, gamma rays, visible light, infrared, microwaves, radio waves

---

3

Which electromagnetic wave has the highest frequency?

A infrared
B microwave
C ultraviolet
D gamma ray

---

4

Which electromagnetic wave has the longest wavelength?

A radio wave
B infrared
C X-ray
D gamma ray

---

5

Which statement is correct for all electromagnetic waves in a vacuum?

A They are longitudinal waves.
B They travel at the same speed.
C They require particles to travel.
D They all have the same wavelength.

---

6

An electromagnetic wave has frequency 6.0 × 10¹⁴ Hz.

Take speed of electromagnetic waves = 3.0 × 10⁸ m/s.

What is its wavelength?

A 2.0 × 10⁻⁶ m
B 5.0 × 10⁻⁷ m
C 1.8 × 10⁶ m
D 2.0 × 10⁶ m

---

7

An electromagnetic wave has wavelength 2.0 × 10⁻² m.

Take c = 3.0 × 10⁸ m/s.

What is its frequency?

A 1.5 × 10⁶ Hz
B 6.0 × 10⁶ Hz
C 1.5 × 10¹⁰ Hz
D 6.0 × 10¹⁰ Hz

---

8

A radio wave has frequency 100 MHz.

Take c = 3.0 × 10⁸ m/s.

What is its wavelength?

A 0.0030 m
B 0.30 m
C 3.0 m
D 300 m

---

9

A microwave has wavelength 12 cm.

Take c = 3.0 × 10⁸ m/s.

What is its frequency?

A 2.5 × 10⁷ Hz
B 2.5 × 10⁸ Hz
C 2.5 × 10⁹ Hz
D 3.6 × 10¹⁰ Hz

---

10

Visible red light has a wavelength of about 700 nm.

Take c = 3.0 × 10⁸ m/s.

What is its frequency?

A 4.3 × 10¹⁴ Hz
B 2.1 × 10¹⁷ Hz
C 4.3 × 10⁵ Hz
D 2.1 × 10⁻¹⁵ Hz

---

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

11

An electromagnetic wave has frequency 7.5 × 10¹⁴ Hz.

Take c = 3.0 × 10⁸ m/s.

Which part of the electromagnetic spectrum is it most likely to be?

A radio wave
B microwave
C visible light
D gamma ray

---

12

An electromagnetic wave has wavelength 1.0 × 10⁻¹⁰ m.

Which type of radiation is it most likely to be?

A radio wave
B infrared
C X-ray
D microwave

---

13

Which wave is used for satellite television communication?

A gamma rays
B microwaves
C ultraviolet
D X-rays

---

14

Which wave is commonly used in TV and radio broadcasting?

A radio waves
B ultraviolet
C X-rays
D gamma rays

---

15

Which wave is used in thermal imaging cameras?

A radio waves
B infrared
C ultraviolet
D gamma rays

---

16

Which wave is used in remote controls for televisions?

A infrared
B X-rays
C gamma rays
D ultraviolet

---

17

Which wave is used to detect broken bones in medical imaging?

A microwaves
B infrared
C X-rays
D radio waves

---

18

Which wave is used to sterilise medical equipment because it is highly penetrating and ionising?

A infrared
B visible light
C gamma rays
D radio waves

---

19

Which wave can cause skin tanning and sunburn?

A radio waves
B microwaves
C ultraviolet
D infrared

---

20

Which type of electromagnetic radiation is most strongly associated with heating food in ovens?

A microwaves
B X-rays
C ultraviolet
D gamma rays

---

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

21

Which type of electromagnetic wave is most likely to be used in optical fibres for communication?

A infrared or visible light
B gamma rays only
C X-rays only
D low-frequency radio waves only

---

22

Which statement correctly compares ultraviolet and infrared radiation?

A ultraviolet has longer wavelength and lower frequency than infrared
B ultraviolet has shorter wavelength and higher frequency than infrared
C ultraviolet and infrared have the same frequency in a vacuum
D infrared is more energetic than ultraviolet

---

23

Which statement correctly compares X-rays and gamma rays?

A gamma rays usually have shorter wavelength and higher frequency than X-rays
B X-rays have longer wavelength than radio waves
C gamma rays are less penetrating than visible light
D X-rays are not electromagnetic waves

---

24

Which electromagnetic waves are ionising and can damage DNA?

A radio waves and microwaves only
B infrared and visible light only
C ultraviolet, X-rays and gamma rays
D radio waves, infrared and visible light only

---

25

Which wave has photons with the greatest energy?

A radio waves
B microwaves
C visible light
D gamma rays

---

26

A student says, “Microwaves have a higher frequency than ultraviolet because they are used for heating.”

Which correction is best?

A Microwaves have lower frequency than ultraviolet.
B Microwaves and ultraviolet have the same frequency.
C Ultraviolet is not part of the electromagnetic spectrum.
D Heating ability proves a wave has the highest frequency.

---

27

Which radiation is most suitable for checking luggage security because it can pass through soft materials but is absorbed more by denser materials?

A X-rays
B infrared
C radio waves
D visible light

---

28

Which electromagnetic wave is most likely to be used for night-vision equipment detecting warm bodies?

A infrared
B ultraviolet
C gamma rays
D radio waves

---

29

Which statement about electromagnetic waves is correct?

A They all travel at 3.0 × 10⁸ m/s in glass.
B They all travel at 3.0 × 10⁸ m/s in a vacuum.
C Gamma rays travel faster than radio waves in a vacuum.
D Radio waves travel faster than light waves in a vacuum.

---

30

An electromagnetic wave has wavelength 3.0 m.

Take c = 3.0 × 10⁸ m/s.

What is its frequency and likely region?

A 1.0 × 10⁸ Hz, radio wave
B 9.0 × 10⁸ Hz, microwave
C 1.0 × 10⁸ Hz, gamma ray
D 1.0 × 10⁻⁸ Hz, radio wave

---

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

31

An electromagnetic wave has wavelength 5.0 × 10⁻⁷ m.

Take c = 3.0 × 10⁸ m/s.

Which pair is correct?

A frequency = 6.0 × 10¹⁴ Hz, visible light
B frequency = 1.5 × 10² Hz, radio wave
C frequency = 6.0 × 10⁻¹⁵ Hz, visible light
D frequency = 1.5 × 10¹⁶ Hz, ultraviolet

---

32

A wave has frequency 3.0 × 10¹⁶ Hz.

Take c = 3.0 × 10⁸ m/s.

What is its wavelength and likely type?

A 1.0 × 10⁻⁸ m, ultraviolet/X-ray region
B 1.0 × 10⁸ m, radio wave
C 9.0 × 10²⁴ m, radio wave
D 1.0 × 10⁻⁴ m, infrared

---

33

Which electromagnetic wave is most likely to have wavelength about 10⁻³ m?

A gamma ray
B X-ray
C microwave
D ultraviolet

---

34

Which electromagnetic wave is most likely to have frequency about 10¹⁹ Hz?

A radio wave
B microwave
C infrared
D X-ray or gamma ray

---

35

Which row correctly links electromagnetic radiation with a use?

	radiation	use
A	infrared	thermal imaging
B	gamma rays	TV remote control
C	radio waves	sterilising surgical instruments
D	ultraviolet	detecting broken bones

---

36

Which row correctly links electromagnetic radiation with a danger?

	radiation	danger
A	radio waves	ionisation of DNA in cells
B	microwaves	internal heating of body tissue
C	visible light	always causes cancer
D	infrared	penetrates bones for imaging

---

37

A microwave oven frequency is 2.45 GHz.

Take c = 3.0 × 10⁸ m/s.

What is the wavelength?

A 0.012 m
B 0.12 m
C 1.2 m
D 12 m

---

38

A mobile phone signal has frequency 900 MHz.

Take c = 3.0 × 10⁸ m/s.

What is its wavelength?

A 0.033 m
B 0.33 m
C 3.0 m
D 33 m

---

39

A source emits electromagnetic waves of wavelength 600 nm.

Take c = 3.0 × 10⁸ m/s.

What is the frequency?

A 5.0 × 10¹⁴ Hz
B 1.8 × 10² Hz
C 5.0 × 10⁵ Hz
D 1.8 × 10¹⁷ Hz

---

40

A student writes these waves in order:

radio → microwave → infrared → visible → ultraviolet → X-ray → gamma

Which quantity increases from left to right?

A wavelength only
B frequency and photon energy
C speed in vacuum
D period

---

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

41

Which quantity decreases from radio waves to gamma rays?

A frequency
B photon energy
C wavelength
D penetrating ability always

---

42

A wave has a period of 2.0 × 10⁻¹⁵ s.

What is its frequency?

A 2.0 × 10⁻¹⁵ Hz
B 5.0 × 10¹⁴ Hz
C 5.0 × 10⁻¹⁴ Hz
D 2.0 × 10¹⁵ Hz

---

43

An electromagnetic wave has period 1.0 × 10⁻⁹ s.

Take c = 3.0 × 10⁸ m/s.

What is its wavelength?

A 0.030 m
B 0.30 m
C 3.0 m
D 3.0 × 10¹⁷ m

---

44

Which pair of electromagnetic waves are both commonly used for communication?

A radio waves and microwaves
B ultraviolet and gamma rays
C X-rays and gamma rays
D infrared and X-rays

---

45

Which pair of electromagnetic waves are both beyond the violet end of the visible spectrum?

A infrared and microwaves
B ultraviolet and X-rays
C radio waves and microwaves
D red light and infrared

---

46

Which pair of electromagnetic waves are both beyond the red end of the visible spectrum?

A ultraviolet and X-rays
B X-rays and gamma rays
C infrared and microwaves
D violet light and ultraviolet

---

47

A hospital uses radiation to kill cancer cells inside the body.

Which radiation is most likely used?

A radio waves
B microwaves
C gamma rays
D visible light

---

48

Why can X-rays be used to image bones?

A bones transmit X-rays more than soft tissue
B bones absorb X-rays more than soft tissue
C X-rays are reflected only by skin
D X-rays travel slower in bones and stop producing images

---

49

A student says, “All electromagnetic waves are dangerous because they are all ionising.”

Which correction is best?

A Only the highest-frequency electromagnetic waves are strongly ionising.
B Radio waves are more ionising than gamma rays.
C Visible light is not electromagnetic radiation.
D Microwaves have the highest photon energy.

---

50

An electromagnetic wave changes from air into glass.

Which quantities definitely change?

A frequency only
B speed and wavelength
C frequency and speed
D frequency, speed and wavelength

---

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

Chapter 17 Answer Key

Q	Ans	Q	Ans	Q	Ans	Q	Ans	Q	Ans
1	B	11	C	21	A	31	A	41	C
2	B	12	C	22	B	32	A	42	B
3	D	13	B	23	A	33	C	43	B
4	A	14	A	24	C	34	D	44	A
5	B	15	B	25	D	35	A	45	B
6	B	16	A	26	A	36	B	46	C
7	C	17	C	27	A	37	B	47	C
8	C	18	C	28	A	38	B	48	B
9	C	19	C	29	B	39	A	49	A
10	A	20	A	30	A	40	B	50	B

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

Detailed Explanations

1. B

• Increasing frequency means moving from the lowest-frequency EM wave to the highest-frequency EM wave.

• Correct order:

  • radio waves

  • microwaves

  • infrared

  • visible light

  • ultraviolet

  • X-rays

  • gamma rays

• So answer is B.

2. B

• Decreasing wavelength means longest wavelength to shortest wavelength.

• This is the same order as increasing frequency:

  • radio waves have the longest wavelength

  • gamma rays have the shortest wavelength

• Answer = B.

3. D

• Gamma rays have the highest frequency in the electromagnetic spectrum.

• Higher frequency also means higher photon energy.

• Answer = gamma ray.

4. A

• Radio waves have the longest wavelength.

• Gamma rays have the shortest wavelength.

• Answer = radio wave.

5. B

• All electromagnetic waves travel at the same speed in a vacuum.

• That speed is approximately:

  • 3.0 × 10⁸ m/s

• They are transverse waves and do not require a medium.

6. B

• Use:

  • v = fλ

  • λ = v / f

• λ = 3.0 × 10⁸ / 6.0 × 10¹⁴

• λ = 0.50 × 10⁻⁶

• λ = 5.0 × 10⁻⁷ m

7. C

• Use:

  • v = fλ

  • f = v / λ

• f = 3.0 × 10⁸ / 2.0 × 10⁻²

• f = 1.5 × 10¹⁰ Hz

• Answer = 1.5 × 10¹⁰ Hz

8. C

• 100 MHz = 100 × 10⁶ Hz = 1.0 × 10⁸ Hz

• λ = v / f

• λ = 3.0 × 10⁸ / 1.0 × 10⁸

• λ = 3.0 m

9. C

• Wavelength = 12 cm = 0.12 m

• f = v / λ

• f = 3.0 × 10⁸ / 0.12

• f = 2.5 × 10⁹ Hz

• Answer = 2.5 × 10⁹ Hz

10. A

• 700 nm = 700 × 10⁻⁹ m = 7.00 × 10⁻⁷ m

• f = v / λ

• f = 3.0 × 10⁸ / 7.00 × 10⁻⁷

• f = 4.3 × 10¹⁴ Hz

• Answer = 4.3 × 10¹⁴ Hz

---

11. C

• Frequency = 7.5 × 10¹⁴ Hz.

• This is around the high-frequency end of visible light, near violet.

• It is much higher than microwaves/radio and far lower than gamma rays.

• Answer = visible light.

12. C

• Wavelength = 1.0 × 10⁻¹⁰ m.

• This is extremely short.

• It is typical of X-rays.

• Radio, microwave and infrared wavelengths are much longer.

13. B

• Satellite television communication commonly uses microwaves.

• Microwaves can pass through the atmosphere and carry high-frequency communication signals.

14. A

• TV and radio broadcasting commonly use radio waves.

• Microwaves can also be used for some communication, but TV/radio broadcasting in this type of MCQ points to radio waves.

15. B

• Thermal imaging detects infrared radiation emitted by warm objects.

• Warmer objects emit more infrared.

• Answer = infrared.

16. A

• TV remote controls commonly use infrared radiation.

• The remote sends infrared pulses to the receiver.

17. C

• X-rays are used to image bones.

• Bones absorb X-rays more strongly than soft tissue.

• This creates contrast on the image.

18. C

• Gamma rays are highly penetrating and ionising.

• They can kill microorganisms, so they are used to sterilise medical equipment.

• They are also used in cancer treatment.

19. C

• Ultraviolet radiation can cause:

  • tanning

  • sunburn

  • skin damage

  • increased risk of skin cancer

• Answer = ultraviolet.

20. A

• Microwave ovens use microwaves.

• Microwaves cause water molecules in food to gain energy, heating the food.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

21. A

• Optical fibres commonly use infrared or visible light.

• The light is guided through the fibre by total internal reflection.

• Gamma rays and X-rays are not used for normal optical fibre communication.

22. B

• Ultraviolet is beyond violet in the spectrum.

• Infrared is beyond red.

• Ultraviolet has:

  • shorter wavelength than infrared

  • higher frequency than infrared

  • higher photon energy than infrared

23. A

• Gamma rays generally have:

  • shorter wavelength than X-rays

  • higher frequency than X-rays

  • higher photon energy than X-rays

• Both are electromagnetic waves.

24. C

• Ionising electromagnetic radiation includes:

  • ultraviolet

  • X-rays

  • gamma rays

• These can damage cells and DNA.

• Radio waves, microwaves, infrared and visible light are generally non-ionising at normal exposure levels.

25. D

• Photon energy increases as frequency increases.

• Gamma rays have the highest frequency.

• Therefore gamma rays have the greatest photon energy.

26. A

• Microwaves have lower frequency than ultraviolet.

• Heating food does not mean a wave has the highest frequency.

• Ultraviolet is much higher frequency and more energetic than microwaves.

27. A

• X-rays are used in luggage security.

• They pass through soft materials more easily but are absorbed more by denser materials.

• This helps reveal hidden objects.

28. A

• Warm bodies emit infrared radiation.

• Night-vision and thermal imaging equipment can detect this infrared radiation.

• Answer = infrared.

29. B

• All electromagnetic waves travel at 3.0 × 10⁸ m/s in a vacuum.

• Gamma rays do not travel faster than radio waves in a vacuum.

• They differ in frequency and wavelength, not vacuum speed.

30. A

• Wavelength = 3.0 m

• f = v / λ

• f = 3.0 × 10⁸ / 3.0

• f = 1.0 × 10⁸ Hz

• A wavelength of metres is in the radio-wave region.

• Answer = 1.0 × 10⁸ Hz, radio wave

---

31. A

• λ = 5.0 × 10⁻⁷ m

• f = v / λ

• f = 3.0 × 10⁸ / 5.0 × 10⁻⁷

• f = 6.0 × 10¹⁴ Hz

• This is visible light.

• Answer = A.

32. A

• f = 3.0 × 10¹⁶ Hz

• λ = v / f

• λ = 3.0 × 10⁸ / 3.0 × 10¹⁶

• λ = 1.0 × 10⁻⁸ m

• This is around the ultraviolet/X-ray region.

• Answer = A.

33. C

• Wavelength about 10⁻³ m = 1 mm.

• This is in the microwave region.

• Gamma rays, X-rays and ultraviolet have much shorter wavelengths.

34. D

• Frequency about 10¹⁹ Hz is extremely high.

• This is in the X-ray or gamma-ray region.

• Radio, microwave and infrared are much lower frequency.

35. A

• Infrared is used for thermal imaging.

• Gamma rays are not used for TV remote controls.

• Radio waves are not used to sterilise surgical instruments.

• Ultraviolet is not used to detect broken bones.

36. B

• Microwaves can cause internal heating of body tissue.

• This is why strong microwave exposure can be dangerous.

• Ionisation of DNA is mainly a danger of ultraviolet, X-rays and gamma rays.

37. B

• Frequency = 2.45 GHz = 2.45 × 10⁹ Hz

• λ = v / f

• λ = 3.0 × 10⁸ / 2.45 × 10⁹

• λ ≈ 0.122 m

• Closest answer = 0.12 m

38. B

• 900 MHz = 900 × 10⁶ Hz = 9.00 × 10⁸ Hz

• λ = v / f

• λ = 3.0 × 10⁸ / 9.00 × 10⁸

• λ = 0.333 m

• Closest answer = 0.33 m

39. A

• 600 nm = 600 × 10⁻⁹ m = 6.00 × 10⁻⁷ m

• f = v / λ

• f = 3.0 × 10⁸ / 6.00 × 10⁻⁷

• f = 5.0 × 10¹⁴ Hz

• Answer = 5.0 × 10¹⁴ Hz

40. B

• Order:

  • radio → microwave → infrared → visible → ultraviolet → X-ray → gamma

• From left to right:

  • frequency increases

  • photon energy increases

  • wavelength decreases

  • period decreases

• Speed in vacuum remains the same.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

41. C

• From radio waves to gamma rays:

  • frequency increases

  • photon energy increases

  • wavelength decreases

• So the quantity that decreases is wavelength.

42. B

• Frequency = 1 / period

• f = 1 / 2.0 × 10⁻¹⁵

• f = 0.50 × 10¹⁵

• f = 5.0 × 10¹⁴ Hz

43. B

• Period = 1.0 × 10⁻⁹ s

• Wavelength = speed × period

• λ = 3.0 × 10⁸ × 1.0 × 10⁻⁹

• λ = 0.30 m

44. A

• Radio waves and microwaves are both commonly used for communication.

• Examples:

  • radio broadcasting

  • television transmission

  • mobile phones

  • satellite communication

  • Wi-Fi

45. B

• Beyond the violet end means higher frequency than visible violet.

• This includes:

  • ultraviolet

  • X-rays

  • gamma rays

• Correct pair = ultraviolet and X-rays.

46. C

• Beyond the red end means lower frequency and longer wavelength than visible red.

• This includes:

  • infrared

  • microwaves

  • radio waves

• Correct pair = infrared and microwaves.

47. C

• Gamma rays are used in radiotherapy to kill cancer cells.

• They are highly penetrating and ionising.

• The danger is real, so treatment must be carefully controlled.

48. B

• Bones absorb X-rays more than soft tissue.

• This creates a shadow/contrast on the detector.

• That is why X-rays can image bones.

49. A

• Not all electromagnetic waves are ionising.

• The highest-frequency waves are strongly ionising:

  • ultraviolet

  • X-rays

  • gamma rays

• Radio waves and microwaves are non-ionising.

50. B

• When an electromagnetic wave enters glass from air:

  • frequency stays the same

  • speed decreases

  • wavelength decreases

• Frequency is fixed by the source.

• So the quantities that definitely change are speed and wavelength.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

---

Common Traps From This Chapter

Trap	Correct Rule
EM spectrum increasing frequency	radio, microwave, infrared, visible, ultraviolet, X-ray, gamma
EM spectrum decreasing wavelength	same order as increasing frequency
Highest frequency	gamma rays
Longest wavelength	radio waves
All EM waves in vacuum	same speed, 3.0 × 10⁸ m/s
EM waves	transverse waves
EM waves in vacuum	do not need particles
Wave equation	v = fλ
MHz	× 10⁶ Hz
GHz	× 10⁹ Hz
nm	× 10⁻⁹ m
Frequency increases	wavelength decreases
Photon energy	increases with frequency
Infrared use	thermal imaging, remote controls, heating
Microwaves use	satellite communication, ovens, mobile signals
Radio waves use	broadcasting, communication
Ultraviolet danger	sunburn, skin damage, DNA damage
X-rays use	bones, luggage security
Gamma rays use	sterilising equipment, cancer treatment
Ionising radiation	UV, X-rays, gamma rays
Bones in X-ray imaging	absorb X-rays more than soft tissue
Air to glass	frequency unchanged, speed and wavelength decrease
In vacuum	gamma rays are not faster than radio waves