# Homework Help: Blue light and resonant frequencies

1. Dec 10, 2013

### AFSteph

Hello again! Just a few multiple choice questions.

When blue light strikes an opaque object whose resonant frequency is the same as the frequency of the blue light what happens? ( Choose as many as apply)
A) The amplitude of the vibrations of the electrons in the object becomes larger
B) The object becomes warm
C) The blue light is absorbed without reemission
D) The blue light is reflected by the electrons in the object
E) The blue light is transmitted through the object

I think A, B, C

When blue light strikes an opaque object whose resonant frequency is lower than the frequency of blue light what happens?
A) The amplitude of the vibrations of the electrons in the object becomes larger
B) The object becomes warm
C) The blue light is absorbed without reemission
D) The blue light is reflected by the electrons in the object
E) The blue light is transmitted through the object

I think D

Which of the following is true of ultraviolet light? (Choose as many as apply)
A) It has a higher frequency than that of visible light
B) Unlike visible light, it is not an electromagnetic wave
C) The Earth's atmosphere is completely opaque to it
D) It is responsible for sunburns.

I think A & D

I don't want you guys to give me the answers, I'd just like to know if I'm understanding this right. Thank you for any assistance :)

Last edited: Dec 10, 2013
2. Dec 11, 2013

### Staff: Mentor

"Resonant frequency"... I guess this means the same as the plasma frequency. Then I agree with (D) in the second question.
How did you get A,B,C in the first question?

The answers to the third question are right.

3. Dec 11, 2013

### nasu

The concept of "Resonant frequency of an object" in this context is not well defined. Resonance of what inside the object? Are you talking about plasma frequency in a metal, as mfb suggested?
Where did you get those questions from?
Without proper context, is hard to say if (and what) you understand.