Topic One - The Solar System And Visible Light

Question 1

What is the geocentric model

Answer 1

The earth in the centre of the universe

Question 2

Who came up with the geocentric model

Answer 2

Ptomely

Question 3

Who came up with the heliocentric model

Answer 3

Copernicus

Question 4

What is the heliocentric model

Answer 4

Sun in the centre of universe

Question 5

What did Galileo discover and how did it contradict ptomelys model

Answer 5

He saw 4 moons orbiting Jupiter, which showed that not everything orbited earth

Question 6

Define wavelength

Answer 6

Distance from one peak to the next

Question 7

Define amplitude

Answer 7

The height of the wave (from the mid line to the peak)

Question 8

Define frequency

Answer 8

How many waves pass a given point each second

Question 9

transverse waves

Answer 9

In transverse waves the vibrations are at 90* to the direction of travel of the wave

Question 10

Longitudinal waves

Answer 10

In longitudinal waves the vibrations are along the same direction as the wave is travelling

Question 11

Refraction and where does it take place

Answer 11

Light travels in straight lines, however it can grange direction when it moves into a different material. Happens at the boundary between two materials

Question 12

Why does a refraction occur

Answer 12

• Because light travels at different speeds in different mediums - faster through air, slower through glass and water
• when moving from air to water/glass, light slows down and ~ refracts towards the normal
  ~ the wavelength decreases
• when moving from water/glass to air, light speeds up
  ~ refracts away from the normal
  ~ wavelength increases

Question 13

Refracting telescopes

Answer 13

. A lens is a transparent block capable of changing the directions of parallel light waves
. Convex lenses
~ curved on both sides - thicker/fatter in the middle
~ converge light rays - focusing them onto a ‘focal point’
~ the distance between the focal point and the lens is called the focal length of the lens
~ the thicker the lens, the greater the converging power of the lens - the shorter the focal length

The focal length of a convex lens can be found by focusing the image of a distant object onto a piece of paper and measuring the distance from the paper to the lens

Question 14

What happens in a refracting telescope

Answer 14

Light rays pass through a convex lens known as the objective lens focusing the image inside the tube
~ the image formed inside the microscope is smaller and is upside down
~ another lens known as the eyepiece lens is used to magnify this image

Question 15

Problems of refracting telescopes

Answer 15

• When light waves reach a boundary between two different materials, not all the light refracts and passes through the material.
  ~ Some is reflected - making the image fainter
• Reflecting telescopes need to be very long to have large magnifications
  ~ large lenses can be used to improve the magnification but they’re heavy and are difficult to make into shape - images have distorted colours

Question 16

How do reflecting telescopes work

Answer 16

• reflecting telescopes use two mirrors to focus the light rays
• when parallel light rays hit the curved primary mirror they reflect back into the tube where they hit a flat secondary mirror
• the image is focused inside the tube
• the eyepiece lens then magnifies the image

Question 17

Comparing reflecting telescopes with refracting telescopes

Answer 17

• the concept of focusing the image inside the tube and then magnifying it using the eyepiece lens is the same as in the refracting telescope
• however, the use of 2 mirrors instead of an objective lens means the image is less faint and allows the telescope to be smaller
• reflecting telescopes are mostly used nowadays because of the need to view very faint, distant stars