diffraction and light

Question 1

diffraction

Answer 1

the spreading of waves after passing through a narrow gap

Question 2

equation for the angle of refraction

Answer 2

sinx = wavelength/length of gap

Question 3

what happens to the rate of diffraction when wavelength decreases

Answer 3

• as wavelength decreases, diffraction decreases
• the wave spreads out less after passing through

Question 4

what 2 things is diffraction dependant on

Answer 4

• the size of the gap (as size decreases, diffraction increases)
• the wavelength (as wavelength decreases, diffraction decreases)

Question 5

why does sound diffract more than light

Answer 5

• the wavelength of light is 1 million times smaller than the wavelength of sound

Question 6

what is Huygens principle

Answer 6

every point on a wave front is a source of wavelets that spread out in the forward direction at the same speed as the wave itself

Question 7

what do the bright fringes represent on a single slit diffraction pattern

Answer 7

they represent areas of maximum light intensity created by constructive interference

Question 8

equation for the angle of diffraction

Answer 8

spacing between slits * sinx = order of maxima * wavelength

Question 9

how does the distance of the laser from the diffraction grating affect the distance between the maxima

Answer 9

the further away the laser is from the diffraction grating, the greater the distance between maxima will be

Question 10

photon

Answer 10

quantum of light

Question 11

equation for planks constant

Answer 11

energy = planks constant x frequency

Question 12

planks constant

Answer 12

6.63x10^34

Question 13

why is violet the first colour you would see on a white light diffraction grating

Answer 13

• violet has the shortest wavelength
• as the path difference increases, the colour changes to red

Question 14

what happens to the excess energy of a photon goes into an electron

Answer 14

• some of the energy goes into freeing the electron
• the excess energy goes into kinetic energy

Question 15

how do you find the work function in a graph

Answer 15

multiply the frequency threshold by the gradient

Question 16

how to carry an experiment to find the work function

Answer 16

• shine light with a specific frequency into the metal
• increase the voltage until it reaches the stopping voltage
• measure the stopping voltage to find the maximum kinetic energy
• use the frequency and kinetic energy to find the work function

Question 17

what is work function

Answer 17

the energy required for an electron to escape the surface

Question 18

equation of work function

Answer 18

hf = work function + KE
energy of the photon = work function + kinetic energy

Question 19

what is the wave model

Answer 19

• energy is shared among all electrons
• if dim light is shone on the electrons, there would be a delay, showing that it is a wave model since electrons have to take time to collect energy and escape

Question 20

what is a photon model

Answer 20

• a specific amount of energy is transferred to an electron
• either the electron overflows, having energy to escape while the remaining energy is transferred to kinetic energy
• or not enough energy is provided for the electron to escape, so it cannot escape

Question 21

what is the relationship between intensity and current

Answer 21

• the amount of photons arriving per second is directly proportional to the rate at which electrons flow
• intensity is directly proportional to current

Question 22

photoelectric effect

Answer 22

• if there are twice as many photons, there are twice as many electrons
• as long as the frequency is greater than the threshold frequency