light - reflection and refraction

Question 1

what makes things visible?

Answer 1

An object reflects light that falls on it.

This reflected light, when received by our eyes, enables us to see things.

Question 2

how do we know light travels in a straight line?

Answer 2

The fact that a small source of light casts a sharp shadow of an opaque object points to this
straight-line path of light, usually indicated as a ray of light.

Question 3

how can we see through a transparent med.?

Answer 3

We are able to see through a transparent medium as light is transmitted through it

Question 4

laws of reflection

Answer 4

1) angle of incidence = angle of reflection

2) IR, RR and N lie on the same plane

Question 5

plane mirror image

Answer 5

• virtual and erect.
• The size of the image is equal to that of the object.
• The image formed is as far behind the mirror
  as the object is in front of it.
• laterally inverted.

Question 6

define spherical mirrors

Answer 6

• part of hollow sphere of glass or polished metal

- The reflecting surface of a spherical mirror may be curved inwards or outwards

Question 7

define concave mirror

Answer 7

spherical mirror whose reflecting surface is curved inward -> ))

Question 8

def. convex mirror

Answer 8

spherical mirror whose reflecting surface is curved outward

Question 9

aperture

Answer 9

diameter of reflecting surface of spher. mirror

Question 10

pole, P

Answer 10

centre of reflecting surface of spher mirror

Question 11

centre of curvature, C

Answer 11

centre of the sphere of which a spherical mirror is a part.

Question 12

radius of curvature, R

Answer 12

radius of sphere of which spher mirror is a part -> frm C to any point on the mirror

Question 13

principal axis, PC

Answer 13

imaginary straight line passing thru C and P

Question 14

principal focus, F

Answer 14

concave - point on princi axis at which all light rays parallel to PC converge after reflection
convex - point on PC FROM which light rays that r parallel to PC APPEAR TO diverge

Question 15

focal length, f

Answer 15

dist between P and F

f=2R

Question 16

reflection

Answer 16

phenomenon in which light rays striking a reflective surface (like mirror) are sent back in the same medium

Question 17

what happens to a ray of light passing thru the centre of curvature of a spher mirror?

Answer 17

cave AND vex - reflected back on the same path

Question 18

what happens to a ray of light passing thru/converging at the focus of a spher mirror?

Answer 18

both - reflected ray is parallel to PC

Question 19

what happens to a ray of light incident at the pole p e of a spher mirror?

Answer 19

reflected back such that <i></i>

Question 20

what happens to a ray of light parallel to the PC of a spher mirror?

Answer 20

cave - passes thru focus

vex - appears to be coming frm the focus

Question 21

refraction of light

Answer 21

when travelling obliquely from one medium to another, the direction of propagation of light in the second medium changes. This phenomenon is known as
refraction of light.