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### Homework Question 1A.3

Posted: Fri Oct 11, 2019 10:29 am
1A.3 asks which of the following happens when the frequency of electromagnetic radiation decreases? Explain your reasoning (a) speed of radiation decreases (b) the wavelength of radiation decreases (c) the extent of change in the electrical field at a given point decreases (d) energy of the radiation increases.

I know the answer is c, but I don't know how to explain the reasoning. A little guidance would be helpful:)

### Re: Homework Question 1A.3

Posted: Fri Oct 11, 2019 12:24 pm
The reason the answer is C is that to cause a change in the electrical field you need a sufficient amount of energy to cause this change. When you decrease the frequency you are decreasing the energy and thus making it more difficult to cause change so there is either less change or no change at all because of the decreased frequency not passing the energy threshold necessary to remove an electron.

It is not (A) because the frequency is not related to speed, it is not (B) because decreasing frequency increases wavelength size, and it is not (D) because by decreasing frequency you are also decreasing energy. Hope this helps

### Re: Homework Question 1A.3

Posted: Fri Oct 11, 2019 12:31 pm
Another way to think about this: if you think of the electrical field as a wave, when the frequency decreases, the wavelength increases so the rate of change (aka the slopes at each point of time) lessens because it's not changing slope as fast as it would be if it had a shorter wavelength. C basically describes the rate of change decreasing, so my first sentence is why C is correct.

### Re: Homework Question 1A.3

Posted: Fri Oct 11, 2019 12:44 pm
To add on to what everyone else was saying,
"a" wouldn't be right because for our purposes, the speed of radiation is constant
"b" wouldn't be right because wavelength and frequency have an inverse relationship, and
"d" wouldn't be right because energy is proportional to frequency