refraction

Question 1

Definition of refraction

Answer 1

Refraction is the bending of light as it passes from one medium to another medium of different optical density

Question 2

Incident Ray

Answer 2

The light ray that hits the reflecting surface

Question 3

Refracted ray

Answer 3

The light ray that enters a medium and undergoes a change of direction

Question 4

Point of incidence

Answer 4

The point at which the incident ray hits the reflecting surface

Question 5

Normal

Answer 5

The imaginary line that is perpendicular to the reflecting surface at the point of incidence

Question 6

Angle of incidence

Answer 6

The angle between the incident ray and the normal

Question 7

Angle of reflection

Answer 7

The angle between the reflected ray and the normal

Question 8

What happens when light travels from an optically less dense to optically denser medium?

Answer 8

Speed of light decreases, light bends towards the normal

Question 9

What happens when light Travels from an optically denser medium to an optically less dense medium?

Answer 9

Speed of light increases, light bends away from the normal

Question 10

Definition of refractive index

Answer 10

Refractive index is the ratio of the speed of light in vacuum to the speed of light in the medium

Question 11

Refractive index formula

Answer 11

Refractive index= speed of light in vacuum (3.0x10^8 ms-1) / speed of light in medium

Question 12

Refractive index and speed of light (10^8 ms-1) in common mediums

Answer 12

• Diamond: 2.40, 1.25
• glass: 1.50,2.00
• water: 1.33, 2.25
• air: 1.000293, 2.999

Question 13

Laws of refraction

Answer 13

1. The incident ray, refracted ray and the normal at the point of incidence all lie in the same plane
2. (Snell’s Law) For the given media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant ie. n1 sin i = n2 sin r

Question 14

Total internal reflection

Answer 14

When an angle of incidence in the glass block is greater than critical angle, the ray will be completely reflected off the flat surface of the block.

Question 15

Critical angle definition

Answer 15

Critical angle is defined as the angle of incidence in an optically denser medium for which the angle of refraction in the optically less dense medium is 90°

Question 16

Calculation for critical angle

Answer 16

N medium= 1 / sin 0c

Question 17

Conditions for total internal reflection

Answer 17

1. The incident ray must travel from an optically denser to an optically less dense medium
2. The angle of incidence must be greater than the critical angle

Question 18

Application of total internal reflection - glass prisms

Answer 18

• Used to reflect light by total internal reflection in some optical instruments such as binoculars, periscopes and single leu’s reflex cameras
• better light reflectors than mirrors because they do not have a silvered surface that can wear off and do not produce multiple reflections

Question 19

Applications of total internal reflection - optical fibres

Answer 19

• Long, thin and flexible; made of glass or plastic and can carry information in the form of coded light pulses
• even when the fibre is bent, light rays entering it will still be internally reflected at the boundary between the two reflective materials
• Rely on total internal reflection of light to transmit signals
• used in endoscope by doctors to inspect the insides of hallow organs such as the digestive tract

Question 20

Advantages of using optical fibers over copper wires in telecommunication

Answer 20

• The data transfer rate is ten to thousand times faster as compared to using copper wires
• there is less signal loss as compared to copper wires
• Optical fibers an lighter and cheaper as compared to copper wires of similar length
• optical fibers can carry much more information over long distances
• optical fibers are immune to electromagnetic interference (eg radio transmitters, power cables adjacent to optical cables and lightning)

Question 21

Advantages of using optical fibers in medicine

Answer 21

• Thin and light. Thus, the endoscopes are kept small for minimally invasive examination and surgery
• flexible. Thus, the endoscopes can curve around obstacles why taking images inside the body