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Modern physics
MDCAT · Physics · 6 questions
Name: ____________________ Date: ____________
The photoelectric effect supports the idea that light behaves as:
- A A purely continuous wave
- B A particle (photons)
- C A sound wave
- D A longitudinal wave
The energy of a photon is given by:
- A E = hf
- B E = qV / t
- C E = mc
- D E = 1/2 mv²
What fraction of a radioactive sample remains after 3 half-lives?
- A 1/8
- B 1/6
- C 1/9
- D 1/3
In beta-minus decay, a neutron changes into:
- A Two protons
- B A proton and a positron
- C A proton, an electron and an antineutrino
- D A helium nucleus
Which type of radiation is the most penetrating?
- A Gamma rays
- B All penetrate equally
- C Alpha particles
- D Beta particles
The mass number of an atom is equal to the number of:
- A Protons plus neutrons
- B Neutrons only
- C Electrons plus protons
- D Protons only
Answer key
1. B, 2. A, 3. A, 4. C, 5. A, 6. A
Light arrives in packets of energy, called photons. A photon of high enough energy can free an electron at once.
E = hf, where h is Planck's constant and f is the frequency of the light.
Each half-life halves the amount: 1/2 x 1/2 x 1/2 = 1/8.
A neutron becomes a proton and the nucleus emits an electron (the beta particle) and an antineutrino.
Gamma rays pass through the body and need thick lead or concrete to be stopped. Alpha particles are stopped by paper.
The mass number counts all nucleons, which are the protons and the neutrons.