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Flashcards in Light & Sound Deck (34)
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1

Light is ..

A form of energy

2

Give the two laws of reflection

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.

3

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

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

4

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

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

5

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

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

6

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

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

7

m = v/u where me =

magnification

8

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

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

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.

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.

10

Refraction:

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

11

Give the two laws of refraction;

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.

12

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

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

13

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

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.

14

n = 1/ ____

n = 1/ sin C

15

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

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

16

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

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

17

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

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

18

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

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

19

For a converging lens, f is always _______.

For a converging lens, f is always positive.

20

For a diverging lens, f is ______.

For a diverging lens, f is negative.

21

The power of a lens: P = _/_

P = 1/ f

22

For two lenses in contact: P = _ + _

P = P1 + P2

23

Accommodation means -

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.

24

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

diverging lens

25

Long sightedness can be corrected by a ________ lens

converging lens

26

Transverse waves are waves which travel ...

... perpendicular to the direction of vibration of the particles.

27

Longitudinal waves are waves which travel...

... parallel to the direction of vibration of the particles.

28

Velocity = _______ x ________.

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

29

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

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

30

Constructive interference occurs when...

two waves combine to give a wave of larger amplitude.

31

Destructive interference occurs when...

two waves meet to give a wave of smaller amplitude.

32

Coherent sources are sources that..

have the same frequency and are in phase.

33

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

diffraction.

34

The longer the wavelength, the _____ the diffraction

greater