wave/particle theory

Question 1

Give the outcomes of Newtons glass prism experiment.

Answer 1

• ray bent & colors separated out on other side.
• light composed of different particles, when combined they form white light
• relationship between color & speed, the more red = slower, the more blue = faster
• relationship of refraction coded into Snell’s Law

Question 2

How does Youngs slots illustrate that light is a wave?

Answer 2

• light source > piece of card with 2 holes > screen > eye
• result = you see bifringent pattern, dark spots turn into bright spots > dark > bright etc
• Huygens diffraction, the pattern seen caused by diffraction of the waves of light interacting destructively- cancelling each other out
• waves can react constructively or destructively depending on phase (how far they are from one another in space)

Question 3

Describe the Hertz experiment.

Answer 3

if you take a circuit with a break in it, it allows e- to jump over & cause a flash (arcing e-). This causes more e- to jump & more flashing

Question 4

Describe an electroscope.

Answer 4

zinc plate with metal rod out the back with a thin piece of gold leaf attached.

Question 5

What happens & why when an electroscope is put in a vacuum and shine different coloured light on it?

Answer 5

the gold leaf floats (electrostatically charged). The height of the leaf floats to is dependent on the color of light that you shine on the box.

• red light: little to no movement
• blue light (UV): movement
• energy is transferred from light to e- in gold leaf, so there is a relationship between color & energy (speed).

Question 6

What did Millikan show when he struck a metal surface with light, causing an e- to be released?

Answer 6

• electrons are bound to the surface of metals by a specific energy, the energy is dependent on the specific metal itself.
• no delay, and not dependent on intensity, just on wavelength & frequency, ie dim blue light & intense blue light produce e- at same speed, but a red light will produce e- at a slower speed than blue light.

Question 7

Momentum =

Answer 7

mass x velocity

Question 8

energy of light =

Answer 8

h x c/ wavelength

Question 9

P or mv =

Answer 9

h/lambda

Question 10

energy =

Answer 10

hF

Question 11

What is a monochromator?

Answer 11

• filters light depending on wavelength

- sun > prism (monochromator) > lens > photographic paper/film

Question 12

energy of photon =

Answer 12

hvc