Light - Light and Reflection

Question 1

What is light?

Answer 1

Light is a form of energy belonging to the electromagnetic spectrum.

Question 2

Reflection

Answer 2

Reflection is the bouncing of light off a surface.

Question 3

Normal

Answer 3

A line perpendicular to a surface. The normal is always drawn 90 degrees to the mirror, at the incident point.

Question 4

Plane

Answer 4

A two dimensional surface.

Question 5

State the two laws of reflection.

Answer 5

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

Question 6

Real image

Answer 6

An image caused by the actual intersection of light rays.

Question 7

Virtual image

Answer 7

An image caused by the apparent intersection of light rays.

Question 8

Parallex

Answer 8

The difference in the apparent position of an object viewed along two different lines of sight.

Question 9

Use of plane mirrors

Answer 9

periscopes, binoculars, viewing yourself.

Question 10

Incident ray

Answer 10

The light ray coming in to the mirror.

Question 11

Reflected ray

Answer 11

The light ray leaving the mirror.

Question 12

Angle of incidence, i

Answer 12

The angle between the incident ray and the normal

Question 13

Angle of reflection, r

Answer 13

The angle between the reflected ray and the normal

Question 14

Specular reflection

Answer 14

A smooth surface reflection. e.g mirror, glass or water

Question 15

Diffuse reflection

Answer 15

Occurs where the light hits an uneven surface.

Question 16

Explain lateral inversion.

Answer 16

When a dance is holding up her left arm, but on the mirror, she is holding up her right arm.

Question 17

Object distance

Answer 17

The distance from a mirror (or lens) to the object.

Question 18

Image distance

Answer 18

The distance from a mirror (or lens) to the image formed.

Question 19

Focal length

Answer 19

The distance from a mirror (or lens) to its focal point.

Question 20

Why do dentist mirror use concave mirrors?

Answer 20

All virtual images produced by concave mirrors are magnified and upright.

Question 21

Why do wing mirrors (in a car) use convex mirrors?

Answer 21

All convex mirror virtual images are diminished and upright, the mirror can show a greater field of view.

Question 22

State the uses of concave mirrors.

Answer 22

• Cosmetic/dentist mirrors

- floodlights

Question 23

State the uses of convex mirrors.

Answer 23

• car mirrors
• concealed junctions
• shops

Question 24

Refraction

Answer 24

The bending of light at a boundary as it passes from one transparent medium to another.

Question 25

True or false. A rare medium is easier for light to pass through.

Answer 25

True

Question 26

True or false. A dense medium is more easier for light to pass through than a rare medium.

Answer 26

True

Question 27

When light travels from a rarer to denser medium, which way does the ray refract to? (Away or towards the normal).

Answer 27

Towards the normal

Question 28

When light travels from a denser to rarer medium, which way does the ray refract to? (Away or towards the normal).

Answer 28

Away from the normal

Question 29

Incident ray

Answer 29

The light ray coming into the medium.

Question 30

Refracted ray

Answer 30

The light ray leaving the medium.

Question 31

Normal

Answer 31

The perpendicular line drawn at the point of incidence of light.

Question 32

Angle of incidence i

Answer 32

The angle between the incident ray and the normal.

Question 33

Angle of incidence r

Answer 33

The angle between the refracted ray and the normal.

Question 34

State the laws of refraction.

Answer 34

1. The incident ray, refracted ray and normal all lie in the same plane.
2. The ratio of the sine of angle of incidence i to the sine of angle of refraction r is a constant. This constant is called the refractive index.

Question 35

What is snell’s law?

Answer 35

The ratio of the sine of angle of incidence i to the sine of angle of refraction r is a constant. This constant is called the refractive index.

Question 36

The refractive index of a medium is always what?

Answer 36

Greater than or equal to 1.

Question 37

The refractive index between two media may what?

Answer 37

May be greater or less than 1 depending on the light ray’s route.

Question 38

The refractive index of a medium.

Answer 38

When the ray of light travels from a vacuum into the medium.

Question 39

The refractive index between two media.

Answer 39

The value of sin i/sin r when the ray of light travels from medium A to medium B.

Question 40

What is the depth ratio?

Answer 40

The closer you look in a vertical straight line to an object, the greater the apparent depth gets. This means that in order to see an image at its most accurate, you need to look straight down at it.

Question 41

What is the critical angle?

Answer 41

The angle of incidence in the the denser medium that results in an angle of refraction of 90 degrees in the rarer medium.

Question 42

What is total internal reflection?

Answer 42

Occurs when a light ray, travelling from a denser to rarer medium at an incident angle greater than the critical angle, is completely reflected.

Question 43

Name the three man parts of the fibre optic and explain their functions.

Answer 43

Core: the glass centre that holds the information transmitted as light

Cladding: this is also usually made of glass but with a lower refractive index than the core, to prevent light escaping.

Buffer Coating: This is usually made of thin but durable plastic.

Question 44

The mechanism by which it transmits light safely and securely is as follows:

Answer 44

1. Light enters the core at an angle greater than the critical angle.
2. The light reflects back and forth as it moves through the fibre, but always staying within the core.
3. This continues for many kilometres until it reaches its source.

Question 45

Name the two errors when dealing with fibre optics.

Answer 45

1. If the optical fibre bends too much, when the light strikes the core surface at an angle less than the critical angle, the light/information will escape.
2. If one optic core touches another, they basically become one medium and allow light to transfer between the two, causing mis-information.

Question 46

What are the advantages of optical fibres over copper cables

Answer 46

1. Optical fibres are cheaper than copper cables over long distances.
2. They are thinner, which allows for more optical bundles.
3. They are more durable, therefore incurring lower replacement and maintenance costs.

Question 47

What are the uses of O.F.C?

Answer 47

Endoscopy: Carry information from camera to lens.
-Enables internal body systems

Surgical Instruments: Dentist drills can have fibre optics tip which can illuminate area.

Information transfer: Broadband information.

Question 48

Explain what are inferior/ superior mirages

Answer 48

• Air split roughly into two layers: a dense cold pocket on top and rare hot pocket of air near ground.
• Reflection of light off the clouds comes through dense cold layer into rare hot layer, it begins to refract away from the normal.
• Bends so much it totally internally reflects back up from the ground.

Superior mirages are the opposite.

Question 49

Explain snell’s window.

Answer 49

When divers are looking up from underwater, they are looking from a dense medium to a rare medium.

• Up to the critical angle, they can see through the water into the air .
• But when the look at angle angle greater than the critical angle, the light is reflected back and they are unable to see through the water.

Question 50

Long-sightedness

Answer 50

When someones is long-sighted, they can see distant objects more clearly than close objects. [too strong]

Question 51

Short-sightedness

Answer 51

When someone is short-sighted, they can see close objects more clearly than distant objects. [too weak]