Light2

Question 1

A Spectrum is

Answer 1

A band of colours that is formed when light is dispersed into its component colours

Question 2

Name the colours in decreasing wavelength

Answer 2

Red
Orange
Yellow
Green
Blue
Indigo
Violet

Question 3

Def a Lens

Answer 3

A piece of any transparent substance that has at least one curved surface

Question 4

Def the Optical Centre

Answer 4

Is the centre of the lens through which light passes without changing direction

Question 5

Def principal axis

Answer 5

Is the straight line passing through the centres of curvature of a lens

Question 6

Def principal focus

Answer 6

Is the POINT to which rays of light travelling parallel to the principal axis converge,
or the point from which they appear to diverge,

After having been refracted by a lens

Question 7

Define Focal Length

Answer 7

Is the distance from the optical centre to the principal focus

Question 8

Def focal plane

Answer 8

Is the line drawn perpendiclarly to the axis at the principal focus

Question 9

Define Magnification

Answer 9

Is the ratio of the size of the image to the size pf the object

Question 10

Name the 2 types of lenses

Answer 10

Converging

Diverging

Question 11

Name 3 different converging lenses

Answer 11

Biconvex

Plano-convex

Concavo-convex

Question 12

Name 3 types of diverging lenses

Answer 12

Biconcave

Plano-concave

Convexo-concave

Question 13

Name 5 differences between Real and Virtual immages

Answer 13

REAL
Light rays pass through the immage

Inverted

Can be projected onto a screen

Is on the opposit side of the lens to the object

Question 14

Draw a ray diagram where the object is on F2. Convex lens

Answer 14

A

Question 15

Give the calculation to work out magnification

Answer 15

Size of image / size of object

Distance of immage / distance of object

Question 16

Compare the eye to a camera

Answer 16

10 comparasons

Eyelid/ shutter. Iris/ diaphrame. Pupil/ appeture. Lens/ lens. Retina./film.
Black melanin choroid/ black of camera

Question 17

Name the two main defects to your eyes associated to lenses

Answer 17

Short-sightedness

Long-sightedness

Question 18

Describe what is wrong with the eye’s lens when a person is long-sighted

Answer 18

Person can see objects far away,but not close-by

The lens is too flat (it has lost its elasticity and does not return to its normal rounded shape. Normally due to old age).

F1 falls behind retina and the image cannot be focussed on the retina

Question 19

How do one rectify far-sightedness

Answer 19

By adding an extra converging lens (using glasses or contact lenses)

The added lens helps to converge the rays a bit more and the eye can then focus the image on the retina

Question 20

What is wrong with the eye’s lens in short-sighted patients.

Answer 20

The lens is too bulbous (cilliary muscle does not pull it flat enough). F1 is too short

The patient can see nearby objects, but far away objects cannot be focussed on the retina, because the image is formed in front of the retina

Question 21

How do they fix short-sightedness

Answer 21

By adding an extra diverging lens

The total focal length gets lengthened

The eye can now accompdate and

Question 22

Define dispersion

Answer 22

It is the splitting up of light into its component colours by refraction.

It occurs because the refractive index of glass is different for each colour