Waves, Optics, Atomic and Nuclear Physics Quiz for AP Physics B & C

Are you getting ready to take the AP physics exam? Before you begin studying, find out what you know and you don't know with these four fundamental quizzes:  Mechanics Quiz for AP Physics B & C , Thermodynamics and Fluid Mechanics Quiz for AP Physics B & C ,  Electricity and Magnetism Quiz for AP Physics B & C , and Waves, Optics, Atomic and Nuclear Physics Quiz for AP Physics B & C

It's okay if you didn't get every question on all of the fundamentals quizzes correct.  The whole point of these quizzes is for you to determine where to focus your study.

It's a common mistake to "study" by doing 20 problems on a topic on which you are already comfortable. But that's not studying … that's a waste of time. You don't need to drill yourself on topics you already understand! It's also probably a mistake to attack what for you is the toughest concept in physics right before the exam. Virtually every student has that one chapter they just don't get, however hard they try. That's okay … (as long as it's only one chapter.)

These fundamentals quizzes can tell you exactly what you should and should not study. Did you give correct answers with full confidence in the correctness of your response? In that case, you're done with that topic. No more work is necessary. The place to focus your efforts is on the topics where either you gave wrong answers that you thought were right, or right answers that you weren't really sure about.

Here is the waves, optics, atomic and nuclear physics quiz.

Problems

1. — When light travels from water (n = 1.3) to glass (n = 1.5), which way does it bend?

— When light travels from glass to water, which way does it bend?

— In which of the above cases may total internal reflection occur?

— Write (but don't solve) an equation for the critical angle for total internal reflection between water and glass.

2. In the equation

,

describe in words what each variable means:

x

m

L

d

l

3. The equation d sin θ = mλ is also used for "light through a slit" types of experiments. When should this equation, rather than the equation in question 2, be used?
4. Describe two principal rays drawn for a convex lens. Be careful to distinguish between the near and far focal points.
   1.  
   2.  
5. Describe two principal rays drawn for a concave lens. Be careful to distinguish between the near and far focal points.
   1.  
   2.  
6. We often use two different equations for wavelength:

.

When is each used?

7. Name the only decay process that affects neither the atomic number nor the atomic mass of the nucleus.

Answers

1. —Light bends toward the normal when going from low to high index of refraction.

—Light bends away from the normal when going from high to low index of refraction.

—Total internal reflection can only occur when light goes from high to low index of refraction.

—sin θ_c = 1.3/1.5

2. x is the distance from the central maximum to any other position, measured along the screen.

m is the "order" of the point of constructive or destructive interference; it represents the number of extra wavelengths traveled by one of the interfering waves.

L represents the distance from the double slit to the screen.

d represents the distance between slits.

l represents the wavelength of the light.

3. 

is used only when distance to the screen, L, is much greater than the distance between bright spots on the screen, x. d sin θ = m λ can always be used for a diffraction grating or double-slit experiment, even if the angle at which you have to look for the bright spot is large.

4. For a convex (converging) lens:
   • The incident ray parallel to the principal axis refracts through the far focal point.
   • The incident ray through the near focal point refracts parallel to the principal axis.
   • The incident ray through the center of the lens is unbent.

[Note that you don't necessarily need to know this third ray for ray diagrams, but it's legitimate.]

5. For a concave (diverging) lens:
   • The incident ray parallel to the principal axis refracts as if it came from the near focal point.
   • The incident ray toward the far focal point refracts parallel to the principal axis.
   • The incident ray through the center of the lens is unbent.

[Note that you don't necessarily need to know this third ray for ray diagrams, but it's legitimate.]

6. 

is used to find the wavelength of a photon only. You can remember this because of the c, meaning the speed of light—only the massless photon can move at the speed of light.



is the de Broglie wavelength of a massive particle. You can remember this because of the m—a photon has no mass, so this equation can never be used for a photon.

7. Gamma decay doesn't affect the atomic mass or atomic number. In gamma decay, a photon is emitted from the nucleus, but because the photon carries neither charge nor an atomic mass unit, the number of protons and neutrons remains the same.