Unit 7: Modern Physics
Physics 2 · Unit 7 · Paper 3

Modern Physics unit test

A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.

Paper 1Paper 2Paper 3
Each paper is built from this unit’s 21 terms and is the same for everyone, so a teacher can assign “Unit 7, Paper 3” and every student sits the identical test. Multiple choice is marked objectively; the written sections you mark yourself against the model answer and rubric.
Suggested time 37 min 34 points0/17 attempted
1

Half-life

2

Work function

3

Stopping potential

4

de Broglie wavelength

5

Radioactive decay is random

6

Emission vs absorption spectra

7

Electron diffraction

8

Conservation in nuclear reactions

9

Alpha, beta and gamma decay

10

Photoelectric graph

11

Wave-particle duality

12

Why binding energy peaks at iron

Short answer 1. Define or explain: Binding energy per nucleon

3 pts

Short answer 2. Define or explain: Energy level diagrams

3 pts

Short answer 3. Define or explain: Photon energy

3 pts

Short answer 4. Define or explain: Why intensity does not eject electrons below threshold

3 pts

Free response

10 pts

This course has no free-response prompt tagged to this unit, so one from elsewhere in the course is used. It is still worth writing — the skill transfers.

A converging lens has a focal length of 12 cm. An object 4.0 cm tall is placed 18 cm from the lens on the principal axis. (a) Calculate the image distance and the image height, and state whether the image is real or virtual and upright or inverted. (b) Describe the principal rays you would draw to locate this image. (c) The object is now moved to 6.0 cm from the lens. Calculate the new image distance and magnification, and describe the image. (d) Explain, using your results, how a converging lens is used as a magnifying glass. (e) A student covers the lower half of the lens with tape. Predict the effect on the image formed in part (a) and justify your prediction.