The Pinhole Dilemma and the Lens

A hole cannot be both sharp and bright

Bending light with Snell's law

What a lens must do

The plan for this module

A pinhole camera is rebuilt with the hole widened to four times its original diameter. The image becomes brighter but blurrier. What is the geometric reason for the blur?

A ray in air meets a flat glass surface with refractive index $n = 1.5$ at an angle of $6$ degrees from the normal. Using the small-angle form $\theta_1 = n \theta_2$, what angle does the ray make inside the glass?

A ray travels in air and meets a glass surface with index $n = 1.5$ at $3$ degrees from the normal. Using the small-angle form $\theta_1 = n\theta_2$, compute the angle inside the glass in degrees and write the number.