Light

Question 0

What is angle of reflection?

Answer 0

r, angle between reflected ray and normal.

Question 1

What is angle of incidence?

Answer 1

i, angle between incident ray and normal.

Question 2

What are the laws of reflection?

Answer 2

1. Incident ray, reflected ray and normal at the point of incidence all lie on the same plane.
2. Angle of incidence,i, is equal to angle of reflection,r.

Question 3

What are the characteristics of image formed by a plane mirror?

Answer 3

1. Virtual
2. Upright.
3. Same size.
4. Laterally inverted.
5. Same distance

Question 4

What is angle of refraction?

Answer 4

r, angle between refracted ray and normal.

Question 5

What is refraction?

Answer 5

Bending of a ray of light as it travels from one medium to another.

Question 6

How does refraction of light occur?

Answer 6

Due to change in speed of light as travels from one medium to another.

Question 7

What happens when a light ray travels through a glass block?

Answer 7

Light travels from a less dense medium(air) to a denser medium(glass), hence speed decreases and it is refracted towards normal.

Question 8

What happens to a light ray traveling from a glass block to air?

Answer 8

Light travels from a denser medium(glass) to a less dense medium(air), it is refracted away from normal.

Question 9

What are the laws of refraction?

Answer 9

1. Incident ray, refracted ray and normal at point of incidence all lie on same plane.
2. For 2 given media, ratio (sin i over sin r) is a constant, where i is angle of incidence and r is angle of refraction. (Snell’s law)

Question 10

What is the refractive index defined as?

Answer 10

Refractive index, n, of medium may be defined as ratio of speed of light in vacuum to speed of light in that medium. (N= speed of light in vacuum over speed of light in medium)

Question 11

What is critical angle?

Answer 11

Defined as angle of incidence in optically denser medium for which angle of refraction in optically less dense medium is 90 degrees.

Question 12

What are the 2 conditions necessary for total internal reflection to occur?

Answer 12

1. Light ray must travel from optically denser medium towards optically less dense medium.
2. Angle of incidence must be greater than critical angle.

Question 13

What are some applications of total internal reflection?

Answer 13

1. Periscope.
2. Binoculars.
3. Fibre optics.

Question 14

How does total internal reflection work in fibre optics?

Answer 14

Fibre optics has relatively high refractive index cylindrical inner core that carries light and a relatively low refractive index outer concentric shell known as cladding

Question 15

Where is fibre optics used in?

Answer 15

Telecommunications.

Question 16

What are the advantages of using fibre optics?

Answer 16

1. Transmit more data.
2. Immune to external electrical interference.
3. Flexible
4. Data can travel more than 10km without need to reamplify.

Question 17

What are the 2 types of thin lenses?

Answer 17

1. Converging lens

2. Diverging lens

Question 18

What is the difference between converging and diverging lenses?

Answer 18

1. Converging lenses are thicker in the middle than at the edge.
2. Diverging lenses are thinner in the middle.

Question 19

Describe the images formed when objects are placed further away than the focal point of a converging lens.

Answer 19

Real and inverted images.

Question 20

Describe the images formed when objects are placed between the focal point and optical centre.

Answer 20

Virtual, upright and magnified images.

Question 21

What is focal length?

Answer 21

f, of a lens is the distance between its optical centre and principal focus