• Support PF! Buy your school textbooks, materials and every day products via PF Here!

Constructive wave interference problem

  • Thread starter throllen
  • Start date
1. Homework Statement

A sheet of glass is coated with a 505nm thick layer of oil (n = 1.42).

For what visible wavelengths of light do the reflected waves interfere constructively/destructively?

2. Homework Equations

For constructive interference

lamba=2nd/m

For destructive interference

lamba=2nd/(m-1/2)

3. The Attempt at a Solution

for constructive

2*1.42*505/(3 or 4) (since m=3 and 4 will give me a visible wavelength) lamba = 717 nm, 478 nm

for destructive

2*1.142*505/(3 or 4 + 1/2) (since m=3 and 4 will also give me a visible wavelength) lamba = 574, 410 nm

HOWEVER, they are wrong... so im completely clueless of what to do next.. help please >.<
 

Doc Al

Mentor
44,766
1,044
Re: Interference

A sheet of glass is coated with a 505nm thick layer of oil (n = 1.42).
Hint: How does the index of refraction of the oil compare to that of the glass. Does it matter?
 
Re: Interference

glass is supposed to have a higher index of refraction.. yes it matters...
 

Doc Al

Mentor
44,766
1,044
Re: Interference

Hmmm... in that case your solution looks fine to me.
 

Related Threads for: Constructive wave interference problem

Replies
1
Views
7K
T
Replies
2
Views
585
Replies
3
Views
47K
Replies
3
Views
4K
Replies
1
Views
663

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top