Science unit 2 grade 8

Question 1

Why does a shadow form?

Answer 1

Because the light rays are being blocked by an opaque object which creates a darker coloured patch with the outline of the object.

Question 2

Where is the trough of a wave?

Answer 2

The trough is the bottom point of the wave.

Question 3

Where is the crest of a wave?

Answer 3

The crest is the top point of the wave.

Question 4

What is the wavelength?

Answer 4

The wavelength is the distance from the crest of a wave to the crest of the wave beside it.

Question 5

What is the frequency of a wave?

Answer 5

The frequency of a wave is how tight together they are. The farther away they are from each other the lower the frequency.

Question 6

What is the amplitude of a wave?

Answer 6

The amplitude of a wave is measured from the centerline of the waves to the crest of the wave.

Question 7

What is the difference between the reflection of rays and refraction of rays?

Answer 7

Reflection is when the light rays rebound right off the surface and goes right back to the same medium. Refraction is when light ray goes through the substance (ie. water) and do not bounce back, they go to a different medium.

Question 8

What are the laws of reflection?

Answer 8

The law of reflection states that the incident ray, the reflected ray, and the normal to the surface of the mirror all lie in the same plane. Furthermore, the angle of reflection is equal to the angle of incidence.

Question 9

What is the difference between and convex lens and a concave lens?

Answer 9

A convex lens curves outwards and the light rays converge to the focal point. (go in and all meet at one spot.) A concave lens is curved inwards and the rays diverge out and never meet at a focal point. (they go away from each other)

Question 10

What is the difference between a concave mirror and a convex mirror?

Answer 10

A concave mirror is curved inwards and the convex mirror is curved out

Question 11

What lenses are used for people who are near sighted?

Answer 11

Concave lenses are used for people who have near sighted vision. So they can only see objects up close but not far away.

Question 12

What type of lens is used for people who are far sighted?

Answer 12

Convex lenses are used for people who are far sighted. So they can only see objects far away but not up close.

Question 13

What is light?

Answer 13

Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be perceived by the human eye.

Question 14

What happens to light when it hits a transparent object?

Answer 14

The light goes through the object. You can see and image but it is a little bit blurry.

Question 15

What happens to light when it hits a translucent object?

Answer 15

You can see certain colours through the object but nothing is clear. You can only see big shapes and colours

Question 16

What happens to light when it hits a opaque object?

Answer 16

The right rebounds right back at you, no light goes through and you can’t see anything.

Question 17

How is frequency and wavelength related?

Answer 17

The longer the wave length, the shorter the frequency is. The shorter the wave length, the higher the frequency.

Question 18

What real life objects use radio, microwave, infrared, visible, ultraviolet, x-ray and gamma rays

Answer 18

Radio waves are used for communication and song radios, microwave waves are used in microwaves, the rays go in and heat up the liquid. Infrared waves are used in night vision goggles. Visible rays are visible to the human eye. Ultraviolet waves are what come out of the sun and give people sun burns. X-ray waves are used in medical x-rays. Gamma waves are used in PET scans

Question 19

Why do colours look the way they are (ie. blue, red, orange)

Answer 19

They look that colour because they reflect the colour they are. Blue object reflect blue waves.