Electromagnetic Waves

Electromagnetic Waves (O Level)

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Question 1
Which of the following has the shortest wavelength?
A
Radio waves
B
Visible Light
C
Microwaves
D
X-rays
Question 1 Explanation: 
In ascending order of wavelengths, the sequence of electromagnetic waves is: gamma rays, X-rays, ultraviolet rays, visible light, infrared radiation, microwaves, radio waves. Out of the four choices, X-rays have the shortest wavelength.
Question 2
Which of the following has the longest wavelength?
A
Radio waves
B
Gamma Rays
C
Ultraviolet rays
D
X-rays
Question 2 Explanation: 
In ascending order of wavelengths, the sequence of electromagnetic waves is: gamma rays, X-rays, ultraviolet rays, visible light, infrared radiation, microwaves, radio waves. Out of the four choices, X-rays have the longest wavelength.
Question 3
Which of the following has the highest frequency?
A
Ultraviolet rays
B
Visible Light
C
Microwaves
D
X-rays
Question 3 Explanation: 
In ascending order of frequency, the sequence of electromagnetic waves is: radio waves, microwaves, infrared radiation, visible light, X-rays, gamma rays. Out of the four choices, X-rays have the highest frequency.
Question 4
Which of the following has the lowest frequency?
A
Radio waves
B
Visible Light
C
Infra-red radiation
D
X-rays
Question 4 Explanation: 
In ascending order of frequency, the sequence of electromagnetic waves is: radio waves, microwaves, infrared radiation, visible light, X-rays, gamma rays. Out of the four choices, radio waves have the lowest frequency.
Question 5
Which of the following uses radio waves?
A
detecting fake notes
B
transmitting communication signals
C
transfer heat
D
killing cancerous cells
Question 5 Explanation: 
Radio waves are used to transmit signal for radio stations, military signal sets, television stations, etc.
Question 6
Which of the following uses microwaves?
  1. microwave oven
  2. transmitting communication signals
  3. detecting flaws in metal
A
1 and 2 only
B
1 and 3 only
C
2 and 3 only
D
1, 2 and 3
Question 6 Explanation: 
Microwaves are used to transmit signals and also to heat things up in a microwave oven.
Question 7
Which of the following uses infra-red radiation?
  1. transfer of heat from a high temperature region to a low temperature region
  2. remote control
  3. killing cancerous cells
A
1 and 2 only
B
1 and 3 only
C
2 and 3 only
D
1, 2 and 3
Question 7 Explanation: 
Infra-red radiation is used in infra-red remote controllers (e.g. TV controllers) and also transmits radiant heat from a higher temperature source to a lower temperature source (see topic on heat transfer)
Question 8
Which of the following uses visible light?
  1. Seeing things with the naked eye.
  2. Transfer of heat from a high temperature region to a low temperature region
  3. Transmitting signals through optical fibres.
A
1 and 2 only
B
1 and 3 only
C
2 and 3 only
D
1, 2 and 3
Question 8 Explanation: 
Visible light is wave that is necessary for us to see things (our eyes can only detect waves at this frequency range) and it is transmitted in optical fibres for telecommunication purposes.
Question 9
Which of the following uses ultraviolet rays?
  1. detecting fake notes
  2. sun tanning
  3. sterlising
A
1 and 2 only
B
1 and 3 only
C
2 and 3 only
D
1, 2 and 3
Question 9 Explanation: 
Ultraviolet (UV) rays will illuminate fluorescent ink that is embedded in real notes. Fake notes do not include such features. UV radiation is needed for the body to manufacture vitamin D but UV rays having high penetration ability can also have a damaging effect on the immune system and cause premature aging of the skin giving it a wrinkled, leathery appearance. UV rays have the ability to affect the function of living cells by altering the structure of the cells nuclear material, or DNA.
Question 10
Which of the following uses X-rays?
  1. Detecting flaws in metals
  2. Detecting restricted objects in the luggage
  3. Detecting bone fracture in human body
A
1 and 2 only
B
1 and 3 only
C
2 and 3 only
D
1, 2 and 3
Question 10 Explanation: 
The soft tissue in our body is composed of smaller atoms and so does not absorb X-rays particularly well. The calcium atoms that make up our bones are much larger, so they are better at absorbing X-rays. X-ray scanners are often used to detect minute flaws in heavy metal equipment due to the penetrating capability of X-rays. X-ray scanners are used in airport security due to the penetrating capability.
Question 11
Which of the following uses gamma rays?
  1. Sterlising
  2. Killing cancerous cells
  3. Detecting flaws in metals
A
1 and 2 only
B
1 and 3 only
C
2 and 3 only
D
1, 2 and 3
Question 11 Explanation: 
Gamma radiation is used to kill micro-organisms, which is called sterlisation. It is used to sterlise food and hospital equipment such as surgical instruments. High intensity gamma radiation will kill cells. It is used in a technique called radiotherapy to treat cancer by targeting the cancer cells with a beam of gamma rays. Radiographic equipment uses penetrating gamma rays to capture images of the internal structure or of a part or finished product.
Question 12
What is the speed of X-ray in vacuum?
A
300 m/s
B
3,00,000 km/s
C
Slightly greater than 3,00,000 km/s
D
Slightly less than 3,00,000 km/s
Question 12 Explanation: 
Speed of electromagnetic waves in vacuum is 3,00,000 km/s
Question 13
Which of the following is/are the properties of electromagnetic waves?
  1. All electromagnetic waves have a speed of 3 x 108 m/s.
  2. All electromagnetic waves are transverse waves
  3. All electromagnetic waves can be seen by the naked eye.
A
1 only
B
2 only
C
1 and 2 only
D
1, 2 and 3
Question 13 Explanation: 
1. All electromagnetic waves have a speed of 3,00,000 km/s. (Incorrect) All electromagnetic waves have a speed of 3,00,000 km/s. in vacuum but not in other medium. 2. All electromagnetic waves are transverse waves. (Correct) 3. All electromagnetic waves can be seen by the naked eye. (Incorrect) Only visible light can be seen by naked eyes.
Question 14
Which of the following is/are the properties of electromagnetic waves?
  1. All electromagnetic waves can be reflected and refracted.
  2. All electromagnetic waves carry energy.
  3. All electromagnetic waves carry charges.
A
1 and 2 only
B
2 and 3 only
C
1 and 3 only
D
1, 2 and 3
Question 14 Explanation: 
1. All electromagnetic waves can be reflected and refracted. (Correct) 2. All electromagnetic waves carry energy. (Correct) 3. All electromagnetic waves carry charges. (Incorrect) All electromagnetic waves do not carry charge.
Question 15
Which of the following statements is true about all electromagnetic waves?
A
They can be detected by a radio aerial.
B
They travel at 3,00,000 km/s.
C
Only sound wave requires a medium to travel.
D
They obey the law of reflection and refraction.
Question 15 Explanation: 
Factual Information
Question 16
Which of the following statements is true about all electromagnetic waves?
A
They can be blocked by solid objects.
B
They cannot be blocked by solid objects.
C
They carry charges.
D
The wave equation v=fλ can be applied to any of the electromagnetic waves.
Question 16 Explanation: 
Factual Information
Question 17
Which of the following waves come after white light in the descending order of wavelengths?
A
infra-red radiation
B
ultra-violet rays
C
microwaves
D
radio waves
Question 17 Explanation: 
In descending order of wavelengths, the sequence of electromagnetic waves is: radio waves, microwaves, infrared radiation, visible light, ultraviolet rays, X-rays, gamma rays. Ultraviolet waves come after visible light.
Question 18
Which colour comes after blue in the descending order of wavelengths?
A
Red
B
Green
C
Yellow
D
Violet
Question 18 Explanation: 
In descending order of wavelength, the sequence of colour spectrum is: red, orange, yellow, green, blue, indigo and violet. Blue comes immediately after green.
Question 19
Which colour comes immediately after green in the ascending order of frequency?
A
Red
B
Green
C
Blue
D
Violet
Question 19 Explanation: 
In ascending order of frequency, the sequence of colour spectrum is: red, orange, yellow, green, blue, indigo and violet. Blue comes immediately after green.
Question 20
Which colour comes immediately after green in the ascending order of wavelength?
  1. Yellow
  2. Blue
  3. Red
A
1 and 2 only
B
2 and 3 only
C
1 and 3 only
D
1, 2 and 3
Question 20 Explanation: 
In ascending order of wavelength, the sequence of colour spectrum is: violet, indigo, blue, green, yellow, orange, red. Yellow and red come after green.
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