The Standard Model 4

Question 1

What is the photoelectric effect

Answer 1

Electrons are ejected from a metal by the action of light. (Photoelectrons are produced by photoemission)

Question 2

What do electroscopes do

Answer 2

They can used to measure charged objects and if the metal plate of the electroscope is charged the gold leaf will rise and if the plate is negatively charged light can be directed at the metal plate to eject electrons

Question 3

What are some importation experimental notes when using a electroscopes

Answer 3

• only -ve charged plates will undergo photoemission. +ve charged plates will not discharged
• even week uv sources will cause the effect
• powerful lasers will not work if under the minimum frequency

Question 4

Explain the photoelectric effect

Answer 4

Only light with a minimum frequency can cause photoemission this minimum frequency is called the threshold frequency. this can only be explained if we treat light as behaving like a particle in this situation. a particle of light is called a photon. This means that the higher the frequency the higher the energy. If photons must have a minimum frequency T eject electrons they must have a minimum energy. This minimum energy is called the work function

Question 5

What happens when a photon has energy above the work function

Answer 5

The excess energy will eject the electron at a higher speed

Question 6

What is the effect of increasing frequency and irradiance

Answer 6

One photon of sufficient energy will eject one electron from the plate. by increasing the irradiance we increase the number of photons. This means the photoelectric current will increase. By increasing the frequency , we do not increase the number of photons. The photoelectric current will not change