# Why are wet things darker?

When something gets wet, it usually appears darker. Why?

# Frosted glass

A parallel beam of light illuminates an object. On the screen, there is an image of his shadow obtained by a lens. If frosted glass is placed between the object and the lens, close to the object, then the image on the screen is the same. If we move the frosted glass closer to the lens, the image gradually blurs and disappears. How do you explain this phenomenon?

# Disappearing Light

A ray of light is incident on the face AB of a prism at a small angle to the normal and emerges through the face BC. The incident angle is slowly reduced. If the ray of light strikes AB normally then no light emerges through BC at all. This is the initial position so that no light emerges through BC. The angle ABC is 400. What is the refractive index of the material of the prism?

# A spacing of the interference fringes on a screen in Young’s experiment

How many times will increase a spacing of the interference fringes on a screen in Young’s experiment (Double-slit experiment), if a green (λ1 = 500 nm) filter is replaced by a red filter (λ2 = 750 nm)?

Image Credit: MIT