light reflection questions

Question

 

1.  when light falls on a surface which is irregular compared to its wavelenth?

 

a.  the reflection is diffuse

b.  glare is produced

c.  the wavelength is refracted

d.  all of these

 

I think a is an answer choice

 

2.  as sunlight shines on a bubble, one wavelenth of blue light is reflected from the inner surface of the soap film.  another wavelength of blue light is reflected from the outer surface of the soap film.  as the waves superimpose they are one-half wavelenth out of phase.  what will you see at that spot on the soap film?

 

a.  very deep blue

b.  no color

c.  yellow

d.  red

 

I say the answer is yellow

 

3.  an interference patterm is produced when

 

a.   both constructive and destructive interference occur

b.  a pattern of light and dark fringes is produced

c.  diffraction occurs

d.  all of these

 

I say the answer is d

Answer 1

I am not positive on the specifics of these, I'd have to go study some, ...

but I think you are right on 1 & 3 and you are wrong on 2.

 

I at first started to try and imaging what was happening, and think of what the diagrams would look like.

Then I realized the key is the statement " as the waves superimpose they are one-half wavelength out of phase".

you are looking at something like:

+ - + - + - + -   superimposed on a wave 180 degrees out of phase as:

- + - + - + - +  and if you add these up you get:

0 0 0 0 0 0 0 0    >>>> in other words they cancel each other out.

Of course I have assumed tat the intensity (amplitude) of both waves is the same

but there is nothing in the question that would sugges otherwise so I think a good assumption.