Electromagnetic Waves & Spectrum Test

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Electromagnetic Waves & Spectrum Test - 4

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Question 1
1 / -0.25

Velocity of plane electromagnetic waves in vacuum equals

A
speed of sound

B
speed of subsonic rockets

C
speed of sonic boom

D
speed of light

Solution

The speed of any electromagnetic waves in free space is the speed of light c = 3x10⁸ m/s. Electromagnetic waves can have any wavelength λor frequency f as long as λf = c.
Question 2
1 / -0.25

Tanning of the skin in sunlight is due to

A
UV radiation

B
visible light

C
infrared

D
cosmic rays

Solution

UVA radiation is what makes people tan. UVA rays penetrate to the lower layers of the epidermis, where they trigger cells called melanocytes (pronounced: mel-an-oh-sites) to produce melanin. Melanin is the brown pigment that causes tanning. Melanin is the body 's way of protecting skin from burning.
Question 3
1 / -0.25

A charged particle oscillates about its mean equilibrium position with a frequency of 10⁹ Hz. Frequency of the electromagnetic waves produced by the oscillator is

A
10⁹

B
600 MHz

C
400 MHz

D
200 MHz

Solution

The frequency of an electromagnetic wave produced by the oscillator is same as that of a charged particle oscillating about its mean position i.e., 10⁹ Hz.
Question 4
1 / -0.25

If the earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now?

A
Lower because the Greenhouse effect of the atmosphere would be absent.

B
Higher as earth has poor reflectivity

C
Higher as the heating is better

D
None of the above

Solution

The radiation of infrared rays of the sun keeps the earth 's surface warm even at night due to the greenhouse effect of the atmosphere. Heavy gases likely CO₂ present in the earth 's atmosphere reflect infra-red radiation back towards the earth 's surface. Due to which earth 's atmosphere becomes richer in infrared radiation. If the atmosphere is absent then earth temperature falls off.
Question 5
1 / -0.25

Do EM waves need a medium to travel through?

A
No

B
Yes

C
ether is required

D
None of the above

Solution

The electromagnetic waves are not mechanical waves. There are vibrations of electric vectors and magnetic vectors in them. These vibrations do not need any particles present in the medium for their propagation. That 's why electromagnetic waves do not require any medium for propagation.This means that electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space.
Question 6
1 / -0.25

Comparing X-rays and Gamma rays

A
Gamma rays are less penetrating than X-rays

B
Gamma rays have larger wavelength than X-rays

C
Gamma rays have more speed than X-rays

D
Gamma rays have more energy than X-rays

Solution

Gamma-ray photons have the highest energy in the EMR spectrum and their waves have the shortest wavelength. Scientists measure the energy of photons in electron volts (eV). X-ray photons have energies in the range 100 eV to 100,000 eV (or 100 keV). Gamma-ray photons generally have energies greater than 100 keV.
Question 7
1 / -0.25

7.5 MHz to 12 MHz band corresponds to wavelength band of

A
40 m –35 m

B
30 m –25 m

C
25 m –22 m

D
40 m –25 m

Solution

f ₁ =7.5 ×10⁶ Hz
f₂ =12 ×10⁶ Hz
λ₁ =c/f₁ =40 m
λ₂ =c/f₂ =25 m

So, the range is 40m to 25m
Question 8
1 / -0.25

The speed of plane electromagnetic waves is maximum in

A
water

B
tourmaline

C
glass

D
vacuum

Solution

The speed of any electromagnetic waves in free space is the speed of light c = 3x10⁸ m/s. Electromagnetic waves can have any wavelength λor frequency f as long as λf = c.
Question 9
1 / -0.25

When white light is split into its component colors by a prism

A
You are not looking at electromagnetic spectrum but at colored light

B
you are looking at a part of the electromagnetic spectrum

C
All of the electromagnetic spectrum

D
None of the above

Solution

when white light enters the prism it has actually entered out atmosphere and so the parts of the EM spectrum like UV don 't appear. After the light comes out of the prism all the parts separate but we can only see the visible part i.e. 400-700nm range. So we look at only a part of the EM spectrum. Hence option B is correct.
Question 10
1 / -0.25

Some scientists have predicted that a global nuclear war on the earth would be followed by a severe ‘nuclear winter ’with a devastating effect on life on earth. What might be the basis of this prediction?

A
Nuclear reactions absorb visible light causing dark days/nights

B
Nuclear reactions absorb atmospheric heat causing cooling

C
The clouds produced by global nuclear war would perhaps cover substantial parts of the sky preventing solar light from reaching many parts of the globe

D
None of the above

Solution

The use of nuclear weapons would cause the formation of smoke clouds preventing the light from the sun reaching earth surface and it will also deplete the atmosphere and therefore stopping the greenhouse effect and thus doubling the cooling effect.
Hence the correct answer is option C.

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Re-Attempt Weekly Quiz Competition

Electromagnetic Waves & Spectrum Test - 4

Result

Electromagnetic Waves & Spectrum Test - 4

Score

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Rank

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SHARING IS CARING

Question 1

speed of sound

speed of subsonic rockets

speed of sonic boom

speed of light

Solution

Question 2

UV radiation

visible light

infrared

cosmic rays

Solution

Question 3

109

600 MHz

400 MHz

200 MHz

Solution

Question 4

Lower because the Greenhouse effect of the atmosphere would be absent.

Higher as earth has poor reflectivity

Higher as the heating is better

None of the above

Solution

Question 5

No

Yes

ether is required

None of the above

Solution

Question 6

Gamma rays are less penetrating than X-rays

Gamma rays have larger wavelength than X-rays

Gamma rays have more speed than X-rays

Gamma rays have more energy than X-rays

Solution

Question 7

40 m –35 m

30 m –25 m

25 m –22 m

40 m –25 m

Solution

Question 8

water

tourmaline

glass

vacuum

Solution

Question 9

You are not looking at electromagnetic spectrum but at colored light

you are looking at a part of the electromagnetic spectrum

All of the electromagnetic spectrum

None of the above

Solution

Question 10

Nuclear reactions absorb visible light causing dark days/nights

Nuclear reactions absorb atmospheric heat causing cooling

The clouds produced by global nuclear war would perhaps cover substantial parts of the sky preventing solar light from reaching many parts of the globe

None of the above

Solution

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