## Question 1A.3

$c=\lambda v$

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nshahwan 1L
Posts: 100
Joined: Fri Aug 30, 2019 12:18 am

### Question 1A.3

Can someone explain this one I just want to make sure I'mg getting it right.
Which of the following happens when the frequency of electromagnetic radiation decreases?
a) The speed of the radiation decreases
b) The wavelength of radiation decreases
c) The extent of the change in the electrical field at a given point decreases
d) The energy of radiation increases

Michelle Shin 4B
Posts: 50
Joined: Thu Jul 25, 2019 12:17 am

### Re: Question 1A.3

Because the waves broaden and the extent of change decreases when the frequency decreases, c is the correct answer.

Anna Chen 1K
Posts: 104
Joined: Thu Jul 25, 2019 12:18 am

### Re: Question 1A.3

The answer is c) The extent of the change in the electrical field at a given point decreases. The electrical field corresponds to the amplitude; as the frequency decreases the waves broaden and the extent of the change decreases.

Cynthia Rodas 4H
Posts: 51
Joined: Wed Sep 18, 2019 12:21 am

### Re: Question 1A.3

I think the best way to approach this problem is to reason through each choice to see why each one does or doesn't happen. So for example:
(a) The speed of radiation doesn't decrease as the frequency of electromagnetic radiation decreases since it is a constant (c= 2.998 x 108 m/s).
(b) The wavelength of radiation can't decrease if the frequency of electromagnetic radiation decreases because they have an inverse relationship. If the frequency decreases, that means there are less complete oscillations. Fewer complete oscillations results in a greater space between the peak-to-peak distance.
(c) The extent of the change in the electrical field at a given point decreases because if the frequency of electromagnetic radiation decreases, then the waves will broaden, meaning the slopes of the wave will also decrease.
(d) The radiation of energy can't increase if the frequency of electromagnetic radiation decreases since they are proportional to each other. Think of the equation E= hv. h is a constant. Therefore the change in energy depends on the frequency. If v decreases, then the amount of energy also decreases. If v increases, then the amount of energy also increases. They have a direct relationship.

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