Reflection

Question 1

Difference between specular and diffuse reflections

Answer 1

Specular - reflections that occur at a smooth, flat surface e.g a mirror

Diffuse - reflections that occur at a rough, uneven surface so the light is scattered. Produces distorted image or no image at all e.g rippling water

Question 2

Define: Incident Ray, Reflected Ray and the Normal

Answer 2

Incident ray - the ray of light hitting the reflective surface.

Reflected ray - the ray of light leaving the reflective surface.

Normal - at a point of incidence (ray hits mirror) a line perpendicular to the surface is the normal.

Question 3

Laws of reflection

Answer 3

Law 1: the incident ray, reflective ray and normal all lie in the same place.

Law 2: the angle of incidence equals the angle of reflection (i=i’).

Law 3: the incident and reflected rays sit on different sides of the normal.

Question 4

Characteristics of an image formed by a plane mirror

Answer 4

The image:

-object size = image size
-object distance = image distance
-same orientation as object
-virtual (cannot be formed on a screen)
-laterally inverted

Question 5

Relationship between angle of rotation of a mirror and angle of rotation of reflected ray

Answer 5

The reflected ray is rotated through twice the angle of rotation of the mirror.
E.g mirror rotated 10degrees, reflected ray rotated 2x10degrees.

Question 6

Describe convex and concave mirrors

Answer 6

Convex mirrors: bulge forward and diverge the light (opposite to concave). Negative effect with a plus radius of curvature.

Concave mirrors: recess inwards and converges light (opposite to convex). Positive effect with a negative radius of curvature.

Question 7

Define (of a curved mirror): pole, centre of curvature, principle axis and radius of curvature

Answer 7

Pole: the centre of a curved mirror.

Centre of curvature: the centre of the hollow sphere of which the mirror is apart of.

Principal axis: the straight line that passes through the centre of curvature and pole of a curved mirror.

Radius of curvature: the radius of the hollow sphere glass of which the mirror is apart of.

Question 8

Define (of convex and concave mirrors): principle focus and focal length

Answer 8

Principal focus: point on the principal axis where the once parallel rays come to a focus after being reflected.

Focal length: the distance between the pole and the principal axis.