optics quest

Question 1

excited atoms are:

Answer 1

atoms within the material of light sources that have absorbed some form of energy and must release it in the form of light.

Question 2

incandescence:

Answer 2

light emitted from a material because of the high temperature of the material.

Question 3

the most abundant source of light is:

Answer 3

the sun.

Question 4

what percentage of the electrical energy used in an incandescent light bulb becomes light?

Answer 4

only five percent; the other 95% is just heat.

Question 5

electric discharge:

Answer 5

when a material emits light from a heated gas or vapour instead of a heated wire.

Question 6

fluorescence:

Answer 6

light that is emitted during exposure of the source to ultraviolet light.

Question 7

what percentage of the energy used in a fluorescent light bulb becomes light?

Answer 7

20%, meaning it is 20% efficient.

Question 8

some examples of fluorescence are:

Answer 8

blood, currency, and fluorescent paint.

Question 9

luminescence:

Answer 9

the emission of light by a material or an object that has not been heated; for example, fluorescence.

Question 10

phosphorescence:

Answer 10

light that is emitted due to the exposure of the source to ultraviolet light, and that continues to be emitted for some time in the absence of the ultraviolet light; for example, glow-in-the-dark objects.

Question 11

chemiluminescence:

Answer 11

light that is produced by a chemical reaction without a rise in temperature; for example, glow sticks.

Question 12

bioluminescence:

Answer 12

light that is produced by a biochemical reaction in a living organism; for example, deep-sea creatures.

Question 13

electromagnetic wave:

Answer 13

light that travels like a wave through empty space and some materials.

Question 14

wavelength:

Answer 14

the distance from one crest of a wave to the next crest.

Question 15

what is the speed of light?

Answer 15

3.00 × 10⁸ m/s.

Question 16

the electromagnetic spectrum:

Answer 16

a diagram that illustrates the range/spectrum of electromagnetic waves in order of wavelength or frequency.

Question 17

which colours have the longest and shortest wavelengths of visible light?

Answer 17

red has the longest wavelength of visible light (700 nm) and violet has the shortest (400 nm).

Question 18

nm:

Answer 18

a nanometer, or 10⁻⁹ (0.000 000 001)

Question 19

the difference between fluorescence and phosphorescence is:

Answer 19

fluorescence stops glowing as soon as the source of radiation is switched off, while the light emitted from phosphoresce will linger after the source of radiation is switched off.

Question 20

reflection:

Answer 20

the change in direction of a light ray when it bounces off a surface.

Question 21

medium:

Answer 21

the substance through which light travels.

Question 22

ray:

Answer 22

a straight line with an arrowhead that shows the direction in which light waves are travelling.

Question 23

Fermat’s Principle:

Answer 23

light will follow the path that takes the least amount of time.

Question 24

incident ray:

Answer 24

a ray of light that travels from a light source toward a surface.

Question 25

angle of incidence:

Answer 25

the angle between the incident ray and the normal in a ray diagram.

Question 26

normal:

Answer 26

a line that’s perpendicular to a surface where a ray of light meets the surface.

Question 27

reflected ray:

Answer 27

a ray that begins at the point where the incident ray and the normal meet.

Question 28

angle of reflection:

Answer 28

the angle between the reflected ray and the normal in a ray diagram.

Question 29

what are the steps to drawing a ray diagram?

Answer 29

1. draw the incident ray.
2. draw the normal by measuring a 90° angle where the incident ray hits the surface.
3. label the incident ray, the reflected ray, the angle of incidence (I), the angle of reflection (r), and the normal.
4. draw the reflected ray from the contact point through the mark.
5. measure the angle of incidence and make a dark to indicate the same angle on the other side of the norma (this is the angle of reflection).

Question 30

Laws of Reflection:

Answer 30

1. the incident ray, the reflected ray, and the normal always lie on the same plane.
2. the angle of reflection, r, is equal to the angle of incidence, i (angle r - angle i)

Question 31

plane mirror:

Answer 31

a mirror with a flat, reflective surface.

Question 32

virtual image:

Answer 32

an image formed by rays that appear to be coming from a certain position, but are not actually coming from this position; the image does not form a visible projection on a screen.

Question 33

what does LOST stand for?

Answer 33

L - location (closer than, farther than, same distance)
O - orientation (upright, inverted)
S - size (same size, larger than, smaller than)
T - type (real or virtual image)

Question 34

what is RADAR?

Answer 34

Radio Detection and Ranging.

Question 35

concave mirror:

Answer 35

a mirror whose reflecting surface curves inwards.

Question 36

principal axis:

Answer 36

on a concave mirror, the line that passes through the center of curvature, C, of the mirror and is normal to the center of the mirror.

Question 37

focal point:

Answer 37

the point on the principal axis through which reflected rays pass when the incident rays are parallel to and near the principal axis.

Question 38

focal length:

Answer 38

the distance between the vertex of a mirror and the focal point; half the distance from the vertex to the center of curvature.

Question 39

real image:

Answer 39

an image that forms when the reflected rays meet.

Question 40

magnification:

Answer 40

the change in size of an optically produced image.

Question 41

spherical aberration:

Answer 41

irregularities in an image in a curved mirror that result when reflected rays from the outer parts of the mirror do not go through the focal point.

Question 42

what’s the difference between a real and virtual image?

Answer 42

real images can be obtained on a screen and are inverted, while virtual images cannot be obtained on a screen and are errect.

Question 43

refraction:

Answer 43

the bending of light as it travels at an angle from a material with one refractive index to a material with a different refractive index.

Question 44

the properties of light that change from one medium to another are:

Answer 44

direction and speed.

Question 45

refracted ray:

Answer 45

the ray that is bent upon entering a second medium.

Question 46

angle of refraction:

Answer 46

the angle between the normal and a refracted ray.

Question 47

the word refract comes from the _____ word ______ and means _______-

Answer 47

refract comes from the Latin word refringere, meaning “to break up”.

Question 48

if a light ray travels from a medium in which its speed is faster to a medium in which its speed is slower, the light ray will bend-

Answer 48

toward the normal.

Question 49

if a light ray travels from a medium in which its speed is slower to a medium in which its speed is faster, the light ray will bend-

Answer 49

away from the normal.

Question 50

index of refraction:

Answer 50

the ratio of the speed of light in a vacuum to the speed of light in a given medium.

Question 51

dispersion:

Answer 51

the process of separating colours by refraction.