Lecture 6 : Newton and the nature of light

Question 1

Escape velocity
* —1— needed by an object to escape the —2—– pull of an object

Answer 1

1) Velocity
2) gravitational

Question 2

Observational evidences of the heliocentric model

• observing the different —1— of Venus, Galileo provided observational evidence to prove the —-2—- mode

Answer 2

1) phases 2)heliocentric

Question 3

Explain how the angular width of the illuminated side of venus as seen from earth changes as venus orbits the sun.

Answer 3

1) when venus on the opposite side of the sun, angular width is smaller, but appears full
2) When between earth and sun, venus is in new phase but has larger angular size
3) on either side, we can see half venus and has an intermediate angular size.

Question 4

Newton and the laws of motion

F = m*–1–
*Every action has an —2– but opposite —-3—-

Answer 4

1)acceleration
2)equal
3)reaction

Question 5

Explain how gravity explains Keplers second law? use picture on slide 141

Answer 5

At A, d is large => gravitational force is small => planet moving slowly but speeding up as d gets smaller

At B, d is small ==> gravitational force is large => planet moving
quickly but slowing down as d gets bigge

Question 6

Newton: ‘—1— light’ or sunlight is a —2— of all the colours of the —-3— (spectrum)

Answer 6

1)white
2)mixture
3)rainbow

Question 7

Refraction: is the —1– of a wave when it enters a medium where its —-2— is different

Answer 7

1)bending
2)speed

Question 8

Light behaves as a wave ==> can travel through the vacuum of space
* But light also behaves as a —-1— called photons that are packets of —-2—– radiation.
* The —-3— of a photon can be calculated using Planck’s law and determines the —4—– (or wavelength) associated with it.

Answer 8

1)particle
2)photons
3)electromagnetic
4)energy
5)frequency