# Two Light Waves Through Plastic

• Dante Tufano
In summary, the conversation discusses the phase difference and interference of two waves of light with a wavelength of 460.0 nm traveling through plastic layers with different refractive indices. The phase difference after emerging from the layers is determined to be 0.212 cycles. The type of interference that occurs at the later position where the waves are brought together is not specified.

#### Dante Tufano

So I'm on my last try for this question, and I could really use some help, I'm completely clueless..

Two waves of light in air, of wavelength λ = 460.0 nm, are initially in phase. They then travel through plastic layers as shown in Figure 35-36, with L1 = 4.00 µm, L2 = 3.50 µm, n1 = 1.20, and n2 = 1.60.

(a) What is their phase difference in cycles after they both have emerged from the layers and arrived at the same horizontal position?
_______________cycles
(b) If the waves at that later position are brought together to a single point, what type of interference occurs?

-closer to destructive interference
-cannot tell from the information given
-closer to constructive interference

2. I know that the change in phase is equal to (L/wavelength)(n-1)

3. I plugged in the given values, and got a phase shift of 4.565 radians for n2 and a shift of 1.739 radians for n1. These added to a shift of 6.304 radians. Since only the decimal matters, it's a shift of .304 radians. However, this is way off, since when I divide by 460nm to get the answer in terms of cycles, I get 661.63, which is wayyyy too large. Even then, I'm clueless on how to answer part b too. Can I please get some help?

Anybody? I really need help with this one..

Anybody?
The slightest help would be amazing

Suppose, when the light enters the plastic sheet, the phase is zero.
The wavelength in the medium of n1 is 391.8 nm.
Number of waves in L1 is 4x10^-6m/391.8 nm. = 10.212
That means 10 full cycles plus 0.212 cycle. Hence phase difference is 0.212 cycle.
Now proceed.

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Dante! Its a small world! This is Doug btw. I can't figure this one out for the life of me...

## 1. What is "Two Light Waves Through Plastic"?

"Two Light Waves Through Plastic" refers to the phenomenon where two light waves pass through a transparent plastic material simultaneously.

## 2. How does light behave when passing through plastic?

When light passes through plastic, it can either be transmitted, absorbed, or reflected. The amount of each behavior depends on the properties of the plastic material.

## 3. What factors affect the behavior of light passing through plastic?

The behavior of light passing through plastic is affected by the properties of the plastic material, such as its density, thickness, and refractive index. The angle at which the light enters and exits the plastic material also plays a role.

## 4. Can light waves change direction when passing through plastic?

Yes, light waves can change direction when passing through plastic due to the refraction of light. This is caused by a change in the speed of light as it travels from one medium to another.

## 5. How is the behavior of light through plastic important in scientific research?

The behavior of light through plastic is important in various scientific research fields, such as optics, materials science, and engineering. Understanding how light interacts with plastic materials can help in the development of new technologies and materials for various applications.