L4 Particles And Radiation- Photons (Overview)

Question 0

What is the wavelength range of Microwaves?

Answer 0

0.1m - 1mm

Question 1

What is the wavelength range of Radio waves?

Answer 1

> 0.1m.

Question 2

What is the wavelength range of Infrared waves?

Answer 2

1mm - 700nm

Question 3

What is the wavelength range of Visible light?

Answer 3

700nm - 400 nm

Question 4

What is the wavelength range of Ultraviolet rays?

Answer 4

400nm - 1nm

Question 5

What is the wavelength range of x-rays and gamma rays?

Answer 5

<1nm

Question 6

At what speed do all EM waves travel at in a vacuum? Include the name and symbol of this speed.

Answer 6

Speed of Light
c
3.0 x 10 (to the power) 8 ms (to the power -1)

Question 7

Light wavelengths are often expressed in what unit?

Answer 7

Nanometers (nm)

Question 8

1nm is the equivalent of how many metres?

Answer 8

0.000000001 m / 10 (to the power) -9 m

Question 9

An electromagnetic wave consists of 2 waves which travel together and vibrate. Name these 2 waves.

Answer 9

Electric wave

Magnetic wave

Question 10

The magnetic wave and the electric wave in an electromagnetic wave travel and what angles to each other and in which direction?

Answer 10

At right angles to each other and to the direction in which they’re travelling.

Question 11

In an electromagnetic wave the electric wave and magnetic wave are in phase with one another. What does this mean?

Answer 11

The 2 waves reach a peak together so they’re in step.

Question 12

Electromagnetic waves are emitted by a …….. particle when it loses energy.

Answer 12

Charged

Question 13

Electromagnetic waves are emitted by a charged particle when it loses energy. When can this happen?

Answer 13

A fast moving electron is stopped/slows down/changes direction.

An electron in shell of an atom moves to a different shell of lower energy.

Question 14

When did Einstein establish the Photon theory?

Answer 14

1905

Question 15

What did Einstein use the Photon theory to explain?

Answer 15

The photoelectric effect- in which electrons are emitted from metal surfaces when light is shone on them.

Question 16

Electromagnetic waves are emitted in short …… of waves, each …….. leaving the source in a different direction. We say it’s ………

Answer 16

Bursts
Burst
Quantised

Question 17

Each burst is a packet of electromagnetic waves and is called a ……… . These travel in ……. lines.

Answer 17

Photon

Straight

Question 18

What happens to an atom’s energy when it emits a photon and how are these energy changes described?

Answer 18

Its energy changes by an amount equal to the photon energy.

Energy changes are discrete amounts/quanta.

Question 19

What is the equation for the energy of a photon?

Answer 19

E=hf

Question 20

What does the symbol h stand for?

Answer 20

Plancks constant - 6.63 x 10 (to the power) -34 Js

Js means Joule seconds

Question 21

What does the f symbol stand for in the E=hf equation? State the unit too.

Answer 21

Frequency

Hz

Question 22

What makes a laser beam very powerful?

Answer 22

Consists of photons of the same frequency (all waves in phase).

Question 23

Power of a laser beam = …………

Answer 23

Energy transferred per second by the photons

Question 24

What is the equation for calculating the power of a laser beam? State what each symbol stands for.

Answer 24

Power of beam= nhf
n = number of photons in beam passing a fixed point each second.
h = plancks constant- 6.63 x 10 (to the power) -34 Js
f = frequency