As the light passes from the air into the glass, it makes an angle θa in air and an angle θl in the lens material, relative to the normal at the surface. what equation relates the angles θl and θa

The angles are related by Snell's Law of refraction.

Step-by-step explanation:

When light is incident on a medium at an angle this angle is known as angle of incidence and it undergoes refraction in the medium at an angle meaning that it deviates from it's normal path this angle of deviation measured with respect to normal is known as angle of refraction and are related by Snell's Law as under

here is the refractive index of material of lens and is the refractive index of air equaling 1  

the last choice

step-by-step explanation:

t = 3

step-by-step explanation:

put t = 3 in this expression :

(3²-1)(3²-2)(3² - 3)(3² - 4) = 8×7×6×5 = 56×30 = 1680