Optics

PY1010 semester 2

laws of reflection

1. Angle of incidence = angle of reflection ( θi = θr)

2. Incident ray, reflected ray & the normal to the surface all line in the same plane.

snells law (reflection)

n1 sin(θ1) = n2 sin(θ2)

N1 & 2: refractive index

θ1 & 2: angle of incidence/ angle of refraction relative to the normal

index of refraction of medium

n = c/v

c (speed of light)

3×10^8 ms

Total internal reflection

when light encounters a boundary, going from medium of high refractive index to medium w lower reflractive index

critical angle of incidence

θc = sin^−1 (n2/n1 )

Convex lense

Focuses light

Concave lens

disperse light

To determine where the image of the object forms

1. The first ray is parallel to the optical axis. This ray goes as far as the centre of the lens,

and it then passes through the focus on the far side of the lens.

2. The second ray passes directly through the middle of the lens.

3. The third ray first passes through the focus on the near side of of the lens and goes as far as the centre of the lens. It then comes out of the lens parallel to the optical axis.

For thin lenses, the object distance, image distance, and focal length are all related by

1/0 + 1/i = 1/f

Magnification

M = hi/h0