Title: Pre-Unit Assessment
Course: MNPCC Physics > Section: Electromagnetic Waves

Use this assessment to see what you know about electromagnetic waves going into the unit.

Q: How do waves used to send information with radios differ from the waves we use in x-ray machines?
- They have different frequencies and wavelengths. (Correct.)
- They have different speed and amplitude. (All electromagnetic radiation travels at the same speed. Amplitude will vary with source, but isn't specific to type.)
- They are different types of waves (transverse vs longitudinal...) (They are all transverse.)
- They travel through different type of media. (All electromagnetic waves do not require a medium to travel.)
A: They have different frequencies and wavelengths.
If right: Your answer is correct.
If wrong: Your answer is incorrect.

Q: What is oscillating in light waves?
- Electric and magnetic fields. (Correct)
- Electric fields. (Magnetic fields as well.)
- Magnetic fields. (Electric fields as well.)
A: Electric and magnetic fields.
If right: Your answer is correct.
If wrong: Your answer is incorrect.

Q: What happens to the speed of light as it goes from air into water?
- It decreases. (Correct.)
- It increases. (Decreases.)
- It does not change. (Only the speed of light in a vacuum is a constant.)
A: It decreases.
If right: Your answer is correct.
If wrong: Your answer is incorrect.

Q: Which ray of light in the diagram below would show how light is reflected off of a mirror?
- Option A (Correct)
- Option B (The angle of incidence always equals the angle of reflection.)
- Option C (The angle of incidence always equals the angle of reflection.)
A: Option A
If right: Your answer is correct.
If wrong: Your answer is incorrect.

Q: An object under water will always appear to be shallower than it actually is because of refraction.  Which of the following paths would show light behavior that would cause objects to appear shallower in water than they actually are?
- Option A (Correct.)
- Option B (That would not change the apparent position.)
- Option C (That would make it look deeper.)
A: Option A
If right: Your answer is correct.
If wrong: Your answer is incorrect.

Q: A green light and an equally intense red light are shown on a white screen.  What color will the screen appear where they overlap?
- Yellow (Correct.)
- White (A component of white light is missing.)
- Brown (This would be the case if you were mixing paints.)
- Blue (Blue is a separate from red and green.)
A: Yellow
If right: Your answer is correct.
If wrong: Your answer is incorrect.

Q: Two note cards are being illuminated by the same light source.  One note card is twice as far away from the light source as the other.  How much less intense is the light on the further note card?
- Four times less intense. (Correct.)
- Two times less intense. (It is a square relationship.)
- Three times less intense. (It is a square relationship.)
A: Four times less intense.
If right: Your answer is correct.
If wrong: Your answer is incorrect.

Q: Which option best describes the path light takes in order for you to see an object?
- Electromagnetic rays that have been reflected off an object enter your eyes. (Correct.)
- Imaging rays leave your eyes and are incident on the object. (No such thing as imaging rays.)
- Electromagnetic rays are emitted from your eyes and are incident upon the object. (This is backwards.)
- Image rays are emitted from the object and enter your eyes. (There is no such thing as image rays.)
A: Electromagnetic rays that have been reflected off an object enter your eyes.
If right: Your answer is correct.
If wrong: Your answer is incorrect.

Q: Which surface would act to bring light rays that reflect off of it together?
- Concave (Correct.)
- Convex (Convex mirrors diverge light.)
- Both (Only concave.)
- Neither (Concave does.)
A: Concave
If right: Your answer is correct.
If wrong: Your answer is incorrect.

Q: Two photons of light are identical in every way except for Photon A has a higher frequency than Photon B.  Which photon has a higher energy?
- Photon A (Correct.)
- Photon B (Energy is directly related to frequency of light.)
- Their energy is identical. (Energy is dependent on frequency.)
A: Photon A
If right: Your answer is correct.
If wrong: Your answer is incorrect.