Week 10

Question 1

Rods

Answer 1

a light-sensitive cell of one of the two types present in large numbers in the retina of the eye, responsible mainly for monochrome vision in poor light.

Question 2

Cones

Answer 2

one of two types of light-sensitive cell in the retina of the eye, responding mainly to bright light and responsible for sharpness of vision and colour perception.

Question 3

Normal

Answer 3

intersecting a given line or surface at right angles

Question 4

Angle of Incidence

Answer 4

the angle which an incident line or ray makes with a perpendicular to the surface at the point of incidence.

Question 5

Angle of reflection

Answer 5

the angle made by a reflected ray with a perpendicular to the reflecting surface.

Question 6

Specular reflection

Answer 6

the mirror-like reflection of light (or of other kinds of wave) from a surface, in which light from a single incoming direction (a ray) is reflected into a single outgoing direction.

Question 7

Diffuse Reflection

Answer 7

reflection of light from a surface such that an incident ray is reflected at many angles rather than at just one angle as in the case of specular reflection.

Question 8

Virtual Image

Answer 8

an optical image formed from the apparent divergence of light rays from a point, as opposed to an image formed from their actual divergence.

Question 9

Convex

Answer 9

having an outline or surface curved like the exterior of a circle or sphere.

Question 10

Concave

Answer 10

having an outline or surface that curves inwards like the interior of a circle or sphere.

Question 11

Index of Refraction

Answer 11

the speed of light in vacuum divided by the speed of light in the medium.
n = c/v

Question 12

Dispersion

Answer 12

the separation of white light into colours or of any radiation according to wavelength.

Question 13

Total internal reflection

Answer 13

the complete reflection of a light ray reaching an interface with a less dense medium when the angle of incidence exceeds the critical angle.

Question 14

Critical angle

Answer 14

the angle of incidence beyond which rays of light passing through a denser medium to the surface of a less dense medium are no longer refracted but totally reflected

Question 15

Convergent (converging) lens

Answer 15

lens such that a beam of light passing through it is brought to a point or focus

Question 16

Divergent (diverging) lens

Answer 16

a lens that causes divergence of rays

Question 17

Presbyopia

Answer 17

long-sightedness caused by loss of elasticity of the lens of the eye, occurring typically in middle and old age.

Question 18

Myopia

Answer 18

the quality of being short-sighted.

Question 19

Diffraction

Answer 19

the process by which a beam of light or other system of waves is spread out as a result of passing through a narrow aperture or across an edge, typically accompanied by interference between the wave forms produced.

Question 20

Polarisation

Answer 20

The direction in which the electrical field of an electromagnetic wave points

Question 21

Coherent Light

Answer 21

is a beam of photons (almost like particles of light waves) that have the same frequency and are all at the same frequency.

Question 22

Laser

Answer 22

a device that generates an intense beam of coherent monochromatic light (or other electromagnetic radiation) by stimulated emission of photons from excited atoms or molecules