26 – Properties of Light

Question 1

photon

Answer 1

electromagnetic radiation described as a particle

electromagnetic radiation can also be described as a wave

Question 2

speed of light

Answer 2

3 × 10⁸ m/s

Question 3

vacuum

Answer 3

empty space

Question 4

light-year

Answer 4

the distance light travels in a year*

*through a vacuum

Question 5

electromagnetic wave

Answer 5

a wave that is partly electric and partly magnetic and carries energy

emitted by vibrating electric charges.

Question 6

electromagnetic spectrum

Answer 6

the range of electromagnetic waves extending from radio waves to gamma rays (low to high frequency)

Question 7

electromagnetic waves from low to high frequency

Answer 7

radio waves

microwaves

infrared

visible light

ultraviolet

x-rays

gamma

Question 8

relationship between frequency and wavelength

Answer 8

inverse

as frequency increases, wavelength decreases

Question 9

visible light from low to high frequency

Answer 9

Red

Orange

Yellow

Green

Blue

Indigo

Violet

Question 10

infrared

Answer 10

electromagnetic waves of frequencies lower than the red of visible light

Question 11

ultraviolet

Answer 11

electromagnetic waves of frequencies higher than those of violet light

Question 12

transparent

Answer 12

term applied to materials that allow light to pass through them in straight lines

Question 13

opaque

Answer 13

term applied to materials that do not allow light to pass through them

Question 14

glass is transparent to…

Answer 14

visible light, but not ultraviolet or infrared

Question 15

how light is absorbed by and re-emitted to neighboring atoms

Answer 15

Question 16

light travels fastest in a…

Answer 16

vacuum

Question 17

ray

Answer 17

a thin beam of light

Question 18

shadow

Answer 18

a shaded region that results when light falls on an object and thus cannot reach into the region on the far side of the object

Question 19

umbra

Answer 19

the darker part of a shadow where all the light is blocked

Question 20

penumbra

Answer 20

a partial shadow that appears where light from part of the source is blocked and light from another part of the source is not blocked

Question 21

polarization

Answer 21

the aligning of vibrations in a transverse wave, usually by filtering out waves of other directions

Question 22

polarization by filtering

Answer 22

unpolarized light becomes polarized by passing through the first filter, which can then be blocked if the second filter is rotated 90° from the first

Question 23

polarization by reflection

Answer 23

light waves that reflect off horizontal surfaces is aligned horizontally (polarized)

sunglasses that are “polarized” are aligned vertically to filter out light waves that reflect off horizontal surfaces

Question 24

3D movies

Answer 24

using two projectors, two images are projected on the screen: one polarized vertically and the other horizontally

these images reflect off the screen to the viewer

the viewer uses special glasses (one lens is polarized vertically and the other lens is polarized horizontally) so that each eye receives only one of the images

Question 25

solar eclipse

Answer 25

an event in which the Moon blocks light from the Sun and the Moon’s shadow falls on part of the Earth

Question 26

lunar eclipse

Answer 26

an event in which the Moon passes into the shadow of Earth