1A.3 Textbook problem


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Jazlyn Romero 1I
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1A.3 Textbook problem

Postby Jazlyn Romero 1I » Sun Oct 25, 2020 6:25 pm

Which of the following happens when the frequency of electromagnetic radiation decreases? Explain your reasoning.
(a) The speed of the radiation decreases.
(b) The wavelength of the radiation decreases.
(c) The extent of the change in the electrical field at a given point decreases.
(d) The energy of the radiation increases.

At first I thought the answer was D, can someone explain the elimination process or why the answer is C?

Jared Limqueco 3E
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Re: 1A.3 Textbook problem

Postby Jared Limqueco 3E » Sun Oct 25, 2020 6:33 pm

So it can't be D because a decrease in frequency results in a decrease in energy. It can't be A because the speed is constant for all waves. It can't be B because frequency and wavelength have an inverse relationship.

I think it's C because when frequency decreases, wavelength increases, and so the slopes of the EM wave is broader. So, the extent of change of the EM wave, which is made up of an electric field wave, decreaes

Melody Haratian 2J
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Re: 1A.3 Textbook problem

Postby Melody Haratian 2J » Sun Oct 25, 2020 6:33 pm

Hi! For the elimination process, the answer cannot be A since the speed of radiation will always be equal to the speed of light ( 3 * 108 m/s ). The answer cannot be B since wavelength and frequency are inversely proportional, so wavelength will increase when frequency decreases. The answer cannot be D since the energy of radiation decreases when frequency decreases. According to the E=hv equation, energy and frequency are directly proportional, so a decrease in frequency will result in a decrease in energy.

The answer is C since the extent to change refers to the slope of the wave. The slope of the wave will decrease in steepness as the wavelength of the wave becomes longer, or the frequency of the wave decreases.

Arya Adibi 1K
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Re: 1A.3 Textbook problem

Postby Arya Adibi 1K » Sun Oct 25, 2020 6:35 pm

Going through each answer choice,

A: Speed of all EM radiation is standard speed of light c, frequency doesn't affect speed
B: The wavelength and frequency of EM radiation are inversely related, so in this scenario wavelength should increase not decrease
C: EM radiation consists of oscillating electric and magnetic fields. The energy of the wave is directly related to the electric field, so if frequency decreases, so does the electric field and energy.
D: Energy and frequency are directly related, if frequency decreases energy should decrease as well.

Hope this helps

jessicaosuna_1F
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Re: 1A.3 Textbook problem

Postby jessicaosuna_1F » Sun Oct 25, 2020 10:56 pm

Hi I believe it is C because as frequency decreases, the wavelength increases and it appears on a graph that the wave is stretched. With this in mind, the change in the electrical field at any point will decrease because the slope has flattened aka the change for any given point isn't as much as before.


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