13.1

Question 1

What is a photon

Answer 1

• Quantum of electromagnetic energy

* [smallest possible] Packet of discrete EM energy

Question 2

What is the Planck constant

Answer 2

6.63 x 10^-34 Js

Question 3

What is an electronvolt

Answer 3

• Energy transferred to or from an electron when it moved through a potential difference of 1V

• Same as elementary charge
-1.60 x 10^-19

Question 4

What is the derivation of 1eV

Answer 4

• W = VQ
• W = (1) x 1.60 x 10^-19
• 1.60 x 10^-19 J

Question 5

What is 1J in eV

Answer 5

• 1J = 6.25 x 10^18 eV

Question 6

How to convert between J and eV

Answer 6

• going TO eV FROM J is MULTIPLY by 1.60 x 10^-19

* going FROM eV TO J is DIVIDE by 1.60 x 10^-19

Question 7

Why can X-rays damage the cells of our bodies

Answer 7

• X-rays have a very short wavelength

• Energy is directly proportional to frequency
• E = hf

• Therefore energy is inversely proportional to wavelength

Question 8

What happens when the LED reaches threshold pd

Answer 8

• When pd reaches threshold pd the LED lights up and starts emitting photons of a specific wavelength

Question 9

What is the relationship for the energy transferred by an electron in the LED

Answer 9

• Threshold pd x charge on electron ≈ energy of emitted photon
• Ve = hf
• eV = hc / lambda

Question 10

A

Answer 10

D