photoelectric effect

Question 1

What was the resolution to the question of the stability of the atom?

Answer 1

The resolution was the assumption that energy is quantized.

Question 2

What issues did the assumption of quantized energy address before the stability of the atom question?

Answer 2

It addressed the issues of blackbody radiation and the photoelectric effect.

Question 3

: What does quantum physics allow physicists to understand about the elements?

Answer 3

Quantum physics allows physicists to understand the properties of the elements from a fundamental point of view.

Question 4

Define a blackbody.

Answer 4

• an enclosure from which very little light can escape, and the light that comes out is in thermal equilibrium.

Question 5

What is the relationship between temperature and the color of light emitted by a body?

Answer 5

-as T increases, the body glows with colors corresponding to ever-smaller wavelengths of the electromagnetic spectrum.
-cooler bodies radiate less energy than warmer bodies

Question 6

What did Max Planck’s trick involve to address the infinite energy prediction (infinite E coming out of blackbody at short wavelengths)?

Answer 6

Max Planck introduced the idea of quantized energy levels for standing waves, represented by E = hf.

Question 7

What was the first and second piece of evidence for quantum physics?

Answer 7

blackbody radiation and photoelectric effect

Question 8

What is the photoelectric effect?

Answer 8

The photoelectric effect is the property of certain metals to emit electrons when illuminated with light of a certain wavelength.

Question 9

What are the emitted electrons called?

Answer 9

photoelectrons

Question 10

What is the work function in the context of the photoelectric effect?

Answer 10

-The work function (E₀) is the amount of energy required to tear an electron away from its orbit.
- the min. amount of E to free an electron

Question 11

How did Einstein resolve the conflict between observation and theory in the photoelectric effect?

Answer 11

Einstein proposed that light is quantized, made of particles called photons.

Question 12

What is the energy of a single photon?

Answer 12

E=hf

Question 13

What does the intensity of light depend on?

Answer 13

The intensity of light depends on the number of photons, with I ∼ nhf.

Question 14

What does increasing the frequency do?

Answer 14

increases the energy

Question 15

What does the current depend on?

Answer 15

the intensity

Question 16

How does increasing intensity affect the photoelectric effect?

Answer 16

Increasing intensity increases the number of emitted electrons but not their energy.

Question 17

What is the condition for electrons to be immediately emitted in very low light intensity?

Answer 17

-as long as a single photon interacts with a single electron
-the energy of the photon is greater than the work function (fc = E₀/h).
hf> E₀

Question 18

What happens when hf >= E₀?

Answer 18

the electrons can’t be ejected from their orbits.