Topic 4

Question 1

What are two properties of all types of waves?

Answer 1

Reflection and refraction

Question 2

What’s the normal

Answer 2

Is a line drawn at 90degreez to the mirror surface at the point that the arriving or incident day meets the mirror. The angles i and r are measured from this line

Question 3

What’s the law of reflection

Answer 3

Angle I=angle r

Question 4

What is refraction

Answer 4

The change in the direction of a light ray that happens when it travels from one transparent material to another

Notice that the ray of light bends towards the normal as it enters the glass and and away from the normal when it leaves the glass

Rays of light that meet a surface at 90 degrees do not bend at all but simply continue into the material without a change in direction

Question 5

Why does refraction happen

Answer 5

Because light waves travel at different speeds in different materials

Question 6

Where does light travel more slowly? In glass or in air?

Answer 6

Travel more slowly in class than they do air

Question 7

What does total internal reflection involve

Answer 7

Both reflection and refraction

Question 8

The role of refraction in total internal refraction

Answer 8

Refraction is when light slows down and usually changes direction when it travels from a less dense to a more dense medium

Light slows down and bends towards the normal when moving from air into glass or water

Question 9

The Role of reflection in total internal reflection

Answer 9

As the angle of incidence increases the angle of refraction will increase until it reaches 90 degrees. At this point the ray of light is travelling along the outer surface of the glass. The angle of incidence is the critical angle.

Above the critical angle the light is totally internally reflected

Question 10

Describe critical angles

Answer 10

Total internal reflection can only occur when travelling from a dense material like glass meets a boundary with a less dense material like air
Light speeds up and changes direction away from the normal when it travels from glass into air
Total internal reflection can take place with sound as well as light

Question 11

What are endoscopes

Answer 11

Can be used to look inside patients’ bodies and make use of optical fibres

Endoscopes allow ‘keyhole’ surgery. This is surgery conducted through a very small cut in the body to speed up recovery time

Question 12

What can happen to couloirs and objects

Answer 12

Transmission reflection and absorption of different wave lengths of light

Question 13

What is specular reflection

Answer 13

Occurs when waves are reflected from a smooth surface

When parallel rays of light are incident on a smooth plane surface such as a mirro the reflected light rays will also be parallel

The size of any irregularities on the surface are much smaller than the wavelength of the wave

Question 14

What is diffuse reflection

Answer 14

Occurs when the surface is not smooth and has rough irregularities
The size of the irregularities is comparable with the wavelength of the wave the incident wave is then reflected at many different angles and the reflected rays will not be parallel such as when light is reflected off a painted wall

Question 15

The colour spectrum

Answer 15

Visible light makes up a very small part of the electromagnetic spectrum

The colours that we see can be split into different colours by a prism

These colours all have a different wavelength, ranging from the longest wavelength at the res end of the spectrum to the shortest wavelength at the violent end

Question 16

Different absorption at surfaces

Answer 16

The colour of an object appears is based on how the atoms at its surface respond to the light being shone on them. A material appears green because its atoms reflect the green wavelengths and absorb all the others

Question 17

What are filters

Answer 17

Let through different colours of light and absorb all the other colours for example, a green filter will let through or ‘transmit’ green light and absorb all of the other wavelengths

Question 18

What are lenses

Answer 18

Pieces of glass that bend light in order to bring it into a focus. Lenses make use of refraction to bend light. The more refraction that occurs the more power the lens has

Question 19

Lenses use refraction to bend light. There are two types of lens. What are they?

Answer 19

Converging

Diverging

Question 20

What’s a converging lens

Answer 20

Bends rays of light towards one another bringing them to a point

Question 21

What’s a diverging lens

Answer 21

Bends rays of light away from each other

Question 22

What is the power of the lens related to

Answer 22

The shape of it

Question 23

When parallel light rays from a distant object pass through a converging lens what happens

Answer 23

They are brought to a focus at a point - the focal point of principal focus. The object can be said to be ‘at infinity’ if it’s distance from the lens is much greater than the focal length of the lens

Question 24

What’s a real image

Answer 24

That can be produced on a screen

The lens focused light rays at the screen

Question 25

What does the focal length depend on

Answer 25

The thickness of the lens and the material that the lens is made from

Question 26

When is a real image formed

Answer 26

Where light rays converge and are actually focused on a screen

Question 27

What’s the nature of s real image

Answer 27

Far from the lens, the real image is upside down and smaller than the object Moving the object closer to the lens causes the image to become larger. The position of the image will move away from the lens but will remain real and upside down At a distance of twice the focal length (2F) the object and image are the same size. Between F and 2F the image is magnified

Question 28

What’s a virtual image

Answer 28

Formed by a converging lens when the object is between the focal point and the lens

Question 29

What’s a diverging lens produce

Answer 29

Virtual image

Question 30

What’s a virtual image

Answer 30

Formed by light rays which appear to diverge from that point but do not actually do so

Question 31

All electromagnetic waves...

Answer 31

Are transverse Travel at same speed in a vacuum (3 x 10^8 m/s) Transfer energy to the observer

Question 32

As the frequency of the radiation increases the wavelength

Answer 32

Decreased

Question 33

What’s the electromagnetic spectrum

Answer 33

``` Radio waves Microwaves Infrared Radiation Visible light Ultra violet X rays Gamma rays ```

Question 34

The refraction of a light ray involves a change in :

Answer 34

The direction of the light ray The speed of the light Light slows down when it moved from air into glass and speeds up when it moves from glass into air The only time when the direction does not change is when the beam is travelling along the normal

Question 35

What are electromagnetic waves composed of

Answer 35

An electric field and a magnetic field at right angles to one another

Question 36

Electromagnetic waves may be :

Answer 36

Reflected off a surface Refracted when they move from one material to another Transmitted when they pass through a material Absorbed by different materials for example UV is absorbed by the skin but not by the earths atmosphere The extent to which these four things happen depends on the material and the wavelength of the EM waves

Question 37

Radio waves and microwaves are both used for

Answer 37

Communicating they have different wavelengths and behave differently in different materials

Question 38

X-rays and gamma-rays cannot reach the surface of the earth as

Answer 38

They are absorbed by the upper atmosphere

Question 39

All objects above ________ will emit electromagnetic radiation

Answer 39

Absolute zero. Their temperature will depend on how much of it they absorb and how much of it they radiate

Question 40

Emitting radiation

Answer 40

A hot cup of tea at 90 degrees will emit radiation that is mainly in the infrared part of the EM spectrum whereas the suns surface temperature of 5700 degrees means that it emits visible light and ultraviolet radiation which have a shorter wavelength than infrared Bodies that are much hotter than the sun will emit x-rays

Question 41

Factors affecting temperature

Answer 41

A body at a constant temperature absorbed the same amount of radiation as it emits An object will increase its temperature if it absorbs more radiation than it emits An object will decrease its temperature if it emits more radiation than it aborbs

Question 42

As the temperature of a body increased ...

Answer 42

More energetic radiation is emitted including infrared visible and UV

Question 43

Intensity and wavelength

Answer 43

Intensity is the energy emitted per square metre per second or the power emitted per square metre, the intensity and wavelength of the radiation emitted by a body depend on its temperature. As the object gets hotter the intensity increases and the wavelength that correspond to the maximum intensity decreased

Question 44

Factors affecting the temperature of the earth

Answer 44

Depends on how much radiation is absorbed and how much is emitted