Need help with light reflection problems

[eku_girl83]

Need urgent help with light reflection problems

Here are my problems:
1) A beam of light has a wavelength of 610 nm in vacuum.
a: What is the speed of this light in a liquid whose index of refraction at this wavelength is 1.45?
I used n=c/v to get 2.07x10^8 m/s. This is correct.
b: What is the wavelength of these waves in the liquid?
I suppose I would use v=lambda*f
v=2.07x10^8 (from part a), but what is f??

2) A ray of light is incident in air on a block of a transparent solid whose index of refraction is n. If n=1.3, what is the largest angle of incidence a for which total internal reflection will occur at the vertical face?

I used sin (crictical angle) = nb/na, where nb=1 and na=1.3. The critical angle is the smallest angle for which total internal reflection occurs. How do I obtain the largest??

Any help would be greatly appreciated!

 

[AntiMagicMan]

Hi

Yes 2.07x10^8m/s is correct.

Remember that the frequency stays constant, so work out the original frequency using c = f* lamda, then insert that frequency into your second formula.

Well total internal refraction occurs for all angles greater than the critical angle... does the light need to carry on undergoing tir like in an optical fibre, if so you can work that out with the help of a simple diagram.

 

[M98Ranger]

Dear student,

I understand that you are facing some difficulties with light reflection problems and you need urgent help. I am here to assist you with your questions to the best of my abilities.

For your first problem, you have correctly used the formula n=c/v to find the speed of light in the liquid. To find the wavelength in the liquid, you can use the formula v=lambda*f. In this case, the frequency (f) remains the same in both vacuum and liquid, so you can use the same value of 610 nm for f. This will give you the wavelength in the liquid as 421 nm.

For your second problem, you have correctly used the formula sin (critical angle) = nb/na to find the critical angle for total internal reflection. In order to find the largest angle of incidence, you can use the formula a = sin^-1 (nb/na). In this case, the largest angle of incidence would be 49.5 degrees.

I hope this helps you with your light reflection problems. If you have any further questions, feel free to reach out to me for assistance. Good luck with your studies!