Chapter 1 Homework Question [ENDORSED]

[Aneesh_Gowri 1H]

The question in the textbook is as follows:

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.

The solutions manual says the answer is C, but I don't understand the relationship between frequency and the change in the electrical field. Can someone please explain this? Thanks!

[Chem_Mod]

Electromagnetic radiation is another word for energy propagated through free space or through a material medium in the form of electromagnetic waves. Therefore, we can think of this as light since it is a type of electromagnetic wave. Looking at the equation for energy per photon of light, , we realize that energy per photon is proportional to frequency. As a result, if frequency decreases, then energy decreases as well, making C the correct answer.

[William Shu 1G]

Personally I don't quite understand the correspondence between energy and "The extent of the change in the electrical field at a given point". Could someone explain this aspect please? Thank you!

[John Hill 4A]

Its just one example of how energy affects the natural world. There are many, raising energy levels in an atom, moving an object, or manipulating an electrical/magnetic field.

[Hadji Yono-Cruz 2L]

Electromagnetic radiation is another word for energy propagated through free space or through a material medium in the form of electromagnetic waves. Therefore, we can think of this as light since it is a type of electromagnetic wave. Looking at the equation for energy per photon of light, , we realize that energy per photon is proportional to frequency. As a result, if frequency decreases, then energy decreases as well, making C the correct answer.

This was a really helpful explanation, thank you for this!!!

[Matthew Mar 1J]

How do we rule out the possibility of a and b? Can we use the formula c=λv and say that wavelength and frequency are inversely related, or does that only apply to light?

[isarose0]

For question 15 in chapter 1B, how does the textbook get part b, I understand why the equation is used (E=h/v) however I don't know how they got 2.5x10^16 for the v used.

[VioletKo3F]

Personally I don't quite understand the correspondence between energy and "The extent of the change in the electrical field at a given point". Could someone explain this aspect please? Thank you!

To clarify, "the extent of change" can be seen as slope. Try drawing it out: one wavelength and another one with lower frequency than the first. You'll find that the slope is significantly lower for the second drawing, so the "extent of the change in the electrical field," or slope, decreases.