Optics Unit Test SCN2D

Question 1

hertz

Answer 1

Frequency is measured in a unit called hertz. It’s defined as cycles per second.

Question 2

EM radiation

Answer 2

One cycle is from peak to peak which is the measurement of wavelength
Ex-> the frequency of red light is 4x10 ^14 which means that red light goes from peak to peak 400,000,000,000,000 times per second

Question 3

What causes sunburn

Answer 3

The sun emits ultraviolet light which damages skin cells and causes sunburn.

Question 4

Sound waves

Answer 4

Sound waves are waves of moving particles and need a medium to pass through
There is no air/particles in space so there is no sound in space

Question 5

Light Waves

Answer 5

Light doesn’t need a medium to travel through so it can travel in space at its maximum speed.
-Light travels in straight lines

Question 6

Incandescence

Answer 6

Light emission from something of high temperature
Ex. Light bulb, fire, stove element

Question 7

Electric discharge

Answer 7

Light emission from passing electric current through a gas
Ex. Lightning, neon sign

Question 8

Phosphorescence

Answer 8

Light emission from something that absorbs UV light and slowly releases it as visible light
Ex. Glow in the dark space stickers

Question 9

Fluorescence

Answer 9

Light emissions from something that absorbs UV light and immediately releases it as visible light
Ex. Fluorescent light bulbs

Question 10

Chemiluminescence

Answer 10

Light emission from a chemical reaction
Ex. Glow sticks, burning magnesium

Question 11

Bioluminescence

Answer 11

Light emission from a chemical reaction within a living organism
Ex. Glow worms, fireflies

Question 12

Triboluminescence

Answer 12

Light emission from certain crystals that are crushed , scratched or rubbed together.
Ex. Indigenous rattles and shakers, lifesavers mints

Question 13

Light Emmiting Diode

Answer 13

Light emission from current flowing through a semiconducting material
Ex. LEDS

Question 14

What are the primary colours

Answer 14

Red, blue, green

Question 15

What are the secondary colours

Answer 15

Yellow, cyan, magenta and white (contains all other colours)

Question 16

Rods

Answer 16

Cells that are receptive to visible light. They are evenly distributed all across the back of the retina. They can’t distinguish colours but they give us our vision at night. Rods are 10x more sensitive to lights than cones. Humans have 120 million rods. The more Rods you have, the better you can see in the dark.

Question 17

cones

Answer 17

Cones are in the fovea. There are about 6.5 million cones in the eye. Humans have red blue and green cones. Some animals have more or less kinds of cones which makes them able to see more or less colours

Question 18

Subtractive colour theory

Answer 18

Pigments absorb certain colours, and allow others to be reflected and thus enter our eyes. A printer seeks to combine magenta, cyan and yellow such that the light being reflected is the colours we want to see, and the light being absorbed is the colours we don’t want to be present in our image.

Question 19

Deer vision

Answer 19

Deers have no red cones which means they see red shades as blue and green shades. They have more rods than humans which means that they have stronger night vision. They also have a greater periferal vision

Question 20

Snake vision

Answer 20

Snakes have photoreceptor cones in their eyes that are sensitive to electromagnetic radiation in the infrared spectrum. Infrared light is thermal energy, which means snakes can “see your body heat”

Question 21

Butterfly vision

Answer 21

Butterflies have photoreceptor cones in their eyes that are sensitive to electromagnetic radiation in the ultraviolet spectrum. Plants reflect ultraviolet light in special patterns that act as signals to guide butterflies to nectar stores.

Question 22

SOLT

Answer 22

S: size (bigger or smaller than object?)
O: Orientation (Upright or inverted?)
L: Location (In refenrence to the focal point, centre of curvature and mirror)
T: Type (Real or virtual Image?)

Question 23

Refraction

Answer 23

Refraction is the bending (or changing direction) of light as it goes from one medium to another.
It happens because the light is changing speed.

Question 24

Law of reflection

Answer 24

Angle of incidence = angle of reflection

Question 25

What makes light bend?

Answer 25

The first is the angle of incidence.
The second is the colour of the light (its wavelength). As the wavelength decreases, the amount of refraction increases. Therefore, light with a short wavelength like violet will refract more than light with a longer wavelength like red.

The third is how dense the medium is. Denser mediums make it so that the photons of light interact with more atoms on its journey through the material, and thus slow down more. This manifests as greater bending of the light.

Question 26

Snells window

Answer 26

If you are underwater the light directly above you will reach you but any light from under the water will undergo total internal reflection, appearing like darkness

Question 27

Mirages

Answer 27

Air above sand is hotter and less dense than cooler air higher up. The different temperatures act like different mediums. Light from the sky hits the critical angle and bens upwards to the eyes. We aren’t imagining water but instead seeing the sky on the sand.

Question 28

Shimmering

Answer 28

Works the same as mirages. Air above a lake is warmer, which causes total internal reflection and overlapping images of the moon onto the water. This looks like a strip of light on the water.

Question 29

Rainbows

Answer 29

Certain colours refract at greater angles than others. White light (suns light), containing all of the colours would hit the water at one angle. Because all colours are in white light, each colour would refract differently and go in its own direction and separate. The light hits the back of the raindrop greater than the critical angle