Light & Sound

Question 1

Light is ..

Answer 1

A form of energy

Question 2

Give the two laws of reflection

Answer 2

1. The angle of reflection (r) equals the angle of incidence (i)
2. The incident ray, the normal and the reflected ray are all in the same plane.

Question 3

A real image is formed by the _____ intersection of light rays. It ______ be formed on a screen and is always ______.

Answer 3

A real image is formed by the actual intersection of light rays. It can be formed on a screen and is always inverted.

Question 4

A virtual image is formed by the ______ intersection of rays. It cannot be formed on a screen and is always _____.

Answer 4

A virtual image is formed by the apparent intersection of rays. It cannot be formed on a screen and is always erect.

Question 5

A concave mirror form a ______ image when the object is ______ the focus.

Answer 5

A concave mirror form a virtual image when the object is inside the focus.

Question 6

1/f = 1/u +1/v 
where;
f =
u= 
and 
v=

Answer 6

f = focal length 
u = the object distance 
v = the image distance

Question 7

m = v/u where me =

Answer 7

magnification

Question 8

_______ mirrors are used as reflectors in headlamps, as makeup mirrors and by dentists

Answer 8

Concave mirrors are used as reflectors in headlamps, as makeup mirrors and by dentists.

Question 9

_______ mirrors give a wide field of view and are used as rear-view mirrors in cars, in buses, in shops and at dangerous junctions.

Answer 9

Convex mirrors give a wide field of view and are used as rear-view mirrors in cars, in buses, in shops and at dangerous junctions.

Question 10

Refraction:

Answer 10

Light bends when it passes from one medium to another medium of different density.

Question 11

Give the two laws of refraction;

Answer 11

1. sin i/ sin r is constant for two given media (Snell’s Law)
   sin i/ sin r is known as the refractive index
2. The incident ray, refracted ray and normal ray are all in the same plane.

Question 12

n = sin _ / sin _ = ____ depth / _____ depth = velocity of medium _ / velocity of light in medium _

Answer 12

n = sin i / sin r = real depth / apparent depth = velocity of medium 1 / velocity of light in medium 2

Question 13

The critical angle is the angle of incidence in the ______ medium corresponding to an angle of refraction of ___ in the _______ medium.

Answer 13

The critical angle is the angle of incidence in the denser medium corresponding to an angle of refraction of 90° in the less dense (rarer) medium.

Question 14

n = 1/ ____

Answer 14

n = 1/ sin C

Question 15

Total internal reflection occurs when the angle of _______ in the ______ medium is greater than the ______ angle.

Answer 15

Total internal reflection occurs when the angle of incidence in the denser medium is greater than the critical angle.

Question 16

_____ ______ ______ is used in periscopes, prism binoculars, reflectors, fibre optics (communication and endoscopes).

Answer 16

Total internal reflection is used in periscopes, prism binoculars, reflectors, fibre optics (communication and endoscopes).

Question 17

A converging lens forms a _____ image only when the object is _____ the focus.

Answer 17

A converging lens forms a virtual image only when the object is inside the focus.

Question 18

A diverging lens always forms a _____, _____, ________ image.

Answer 18

A diverging lens always forms a virtual, erect, diminished image.

Question 19

For a converging lens, f is always _______.

Answer 19

For a converging lens, f is always positive.

Question 20

For a diverging lens, f is ______.

Answer 20

For a diverging lens, f is negative.

Question 21

The power of a lens: P = /

Answer 21

P = 1/ f

Question 22

For two lenses in contact: P = _ + _

Answer 22

P = P1 + P2

Question 23

Accommodation means -

Answer 23

Accommodation means that the eye focuses objects at different distances from it onto the retina by changing the shape, and consequently the focal length, of the lens.

Question 24

Short sightedness (myopia) can be corrected by a ________ lens.

Answer 24

diverging lens

Question 25

Long sightedness can be corrected by a ________ lens

Answer 25

converging lens

Question 26

Transverse waves are waves which travel …

Answer 26

… perpendicular to the direction of vibration of the particles.

Question 27

Longitudinal waves are waves which travel…

Answer 27

… parallel to the direction of vibration of the particles.

Question 28

Velocity = _______ x ________.

Answer 28

Velocity = frequency x wavelength ( c = f x λ )

Question 29

Interference means that when two or more waves meet, the resultant displacement equals….

Answer 29

Interference means that when two or more waves meet, the resultant displacement equals the algebraic sum of the individual displacements.

Question 30

Constructive interference occurs when…

Answer 30

two waves combine to give a wave of larger amplitude.

Question 31

Destructive interference occurs when…

Answer 31

two waves meet to give a wave of smaller amplitude.

Question 32

Coherent sources are sources that..

Answer 32

have the same frequency and are in phase.

Question 33

The spreading of waves into the geometric shadow of an obstacle is called _______.

Answer 33

diffraction.

Question 34

The longer the wavelength, the _____ the diffraction

Answer 34

greater