# Physics

What is the thinnest soap film (excluding the case of zero thickness) that appears black when illuminated with light with a wavelength of 515 nm ? The index of refraction of the film is 1.32, and there is air on both sides of the film.

--------------

I know that it would appear dark when there is destructive reflection, the equation for which is:
2t = (m + .5)lambda (where t is thickness, and no phase shift)
but I don't know how to incorporate the index of refraction n for air etc.
Any help would be appreciated, thanks

1. 👍
2. 👎
3. 👁
1. lambda is speedlight/freq

lambda in soap= (c/1.5)(1/c/515nm)=515nm/1.5

1. 👍
2. 👎
👤
bobpursley

## Similar Questions

1. ### physics

A cake of soap placed in a bathtub of water sinks. The buoyant force on the soap is: a- Zero b- Less than its weight c- Equal to its weight d- More than its weight I believe is D for if the cake of soap sinks, it means that the

2. ### Solar Energy Help ASAP

In the figure below the absorption coefficient as a function of the wavelength for several semiconductor materials is presented. Let's consider monochromatic light of photons with energy of Eph=1.55eV that incidents a film with

3. ### Statistics

Thickness measurements of ancient prehistoric Native American pot shards discovered in a Hopi village are approximately normally distributed, with a mean of 4.9millimeters (mm) and a standard deviation of 1.5 mm. For a randomly

4. ### Science

A drop of oil of volume 10^10m spread out on water to make a circular film of radius 10^1m. What is the thickness of the film

1. ### chemistry

A laundry can purchase soap containing 30% water for a price of \$0.30/kg FOB the soap manufacturing plant (i.e., at the soap plant before shipping costs, which are owed by the purchaser of the soap). It can also purchase a

2. ### Physics

Problem 17.26 A thin film of (MgF2) n= 1.38 coats a piece of glass. Constructive interference is observed for the reflection of light with wavelengths of 500nm and 625nm . Part A - What is the thinnest film for which this can

3. ### Physics

What is the thinnest film of a coating with n=1.42 on glass n=1.52 for which destructive interference of the red component (650 nm) of an incident white light beam in air can take place by reflection? I am confused on the n's and

4. ### PHYSICS thankyou in advance...

A cake of soap placed in a bathtub of water sinks. The buoyant force on the soap is: a- Zero b- Less than its weight c- Equal to its weight d- More than its weight I believe is D for if the cake of soap sinks, it means that the

1. ### Physics

A drop of oil of 10^10m spread out on water to make a circular film of radius 10^1m. What is the thickness of the film.

2. ### physics

The relative density of oil is 0.5 of mass 0.5g forms a film of area 0.25.calculate the thickness of the oil film.

3. ### Physics (light)

A soap film is viewed in white light. If the film is much thinner than the wavelength of blue light, what is the appearance of the film? The soap film appears totally transparent because it reflects no visible light. The soap film

4. ### Physics

A 2.0-cm thich bar of soap is floating on a water surface so that 1.5 cm of the bar is under water. Bath oil of specific gravity 0.60 is poured into the water and floats on top of it. What is the depth of the oil layer when the