LT: reflection

Question 1

what is reflection?

Answer 1

the bouncing of light off a surface

Question 2

why does an apple appear red under sunlight?

Answer 2

except for red light, pigments on the apple absorb other colours of light, so only red light is reflected off the apple into an observer’s eye.

Question 3

what happens when blue light is incident on a red apple?

Answer 3

the pigments on the apple will absorb all blue light, thus no light is reflected off the apple.

Question 4

can you see an apple with no light source? why or why not?

Answer 4

no. since there is no light source, no light will be reflected off the apple into an observer’s eyes.

Question 5

characteristics of image formed by plane mirror (5)

Answer 5

1. the image is of the same size as the object
2. the image is upright
3. the perpendicular object distance is equal to the perpendicular image distance from the plane mirror
4. the image is laterally inverted
5. the image is virtual

Question 6

define incident ray

Answer 6

the incident ray is the light ray hitting the reflecting surface

Question 7

define angle of incidence

Answer 7

angle of incidence, i: the angle between the incident ray and the normal

Question 8

define the normal

Answer 8

normal: the line perpendicular to the surface at the point of incidence

Question 9

define angle of reflection

Answer 9

angle of reflection, r: the angle between the reflected ray and the normal

Question 10

define reflected ray

Answer 10

the reflected ray is the light ray travelling away from the reflecting surface after bouncing off the surface

Question 11

laws of reflection (2)

Answer 11

1. the incident ray, reflected ray and normal at the point of incidence all lie in the same plane
   2: angle of incidence, i, is equal to the angle of reflection, r (i=r)

Question 12

what are concave mirrors? how do images formed by concave mirrors look like?

Answer 12

mirrors with a curved surface that bends inwards.

images formed by concave mirrors are virtual, upright and magnified. (commonly used when magnified image is needed)

Question 13

what are convex mirrors? how do images formed by convex mirrors look like?

Answer 13

mirrors with a curved surface that bends outwards.

images formed by convex mirrors are virtual, upright and diminished. they provide a wide field of vision (commonly used to view a wide area)

Question 14

describe regular reflection

Answer 14

on a smooth surface,
the angles of incidence on all the points of incidence are the same,

thus the angles of reflection are the same
as the light beam is evenly reflected.

the observer will be able to see the image clearly, and the reflecting surface will appear brightly lit.

Question 15

describe diffused reflection

Answer 15

on a rough surface,

each point of incidence has a different normal from that at other points,

and the angle of incidence at every point of incidence may be different.

hence, the angles of reflection made by the reflected rays are different,
so the reflected rays will no longer form a beam of parallel rays.

the observer will not see the reflected image as clearly, and the reflecting surface will not appear as brightly lit.