Refraction - AP Physics 2

1. What is the effect of refraction on a straight object in water?

   The object appears bent or displaced at the surface. Light bends at the interface, creating optical illusion.

2. What happens to the speed of light as it enters a denser medium?

   The speed of light decreases. Light slows down in optically denser media.

3. Calculate the wavelength in glass ($n=1.5$) if $\text{wavelength in air} = 600 \text{nm}$.

   $\text{Wavelength in glass} = \frac{600 \text{nm}}{1.5}$. Wavelength scales inversely with refractive index.

4. What is the relationship between refractive index and optical density?

   Higher refractive index means higher optical density. Higher $n$ means light travels slower in that medium.

5. Find the critical angle for water-air interface with $n_{\text{water}} = 1.33$.

   $\theta_c = \text{sin}^{-1}(\frac{1}{1.33})$. Uses $\theta_c = \sin^{-1}(\frac{n_2}{n_1})$ with $n_2 = 1$.

6. Identify the phenomenon when light passes through a prism.

   Dispersion occurs, separating light into colors. Different colors refract at different angles through prism.

7. What is the refractive index of a vacuum?

   The refractive index of a vacuum is 1. Vacuum is the reference medium with $n = 1$.

8. What is the formula for the refractive index in terms of speed?

   $n = \frac{c}{v}$. Defines refractive index as ratio of speeds.

9. What is the main cause of chromatic aberration in lenses?

   Chromatic aberration is caused by dispersion. Different colors focus at different points due to dispersion.

10. How does wavelength change when light enters a denser medium?

    Wavelength decreases. Frequency stays constant, so $\lambda = \frac{v}{f}$ decreases as $v$ decreases.

11. What occurs when light passes from a less dense to a more dense medium?

    Light bends toward the normal. Higher optical density causes light to bend toward the normal.

12. Find the angle of refraction for light moving from air to water at $45^\text{o}$. ($n_{\text{water}}=1.33$)

    $\theta_2 = \text{sin}^{-1}(\frac{\text{sin}(45^\text{o})}{1.33})$. Light bends toward normal when entering denser medium.

13. What is the apparent depth of an object underwater?

    Apparent depth is less than actual depth due to refraction. Light bends away from normal when exiting water.

14. What is the principle of reversibility in refraction?

    Light will follow the same path if its direction is reversed. Light paths are reversible due to symmetry of physics.

15. Which color of light refracts the least?

    Red light refracts the least. Red has lowest frequency and refracts least.

16. Which color of light refracts the most?

    Violet light refracts the most. Violet has highest frequency and refracts most.

17. What is the definition of refraction?

    Refraction is the bending of light as it passes from one medium to another. Light changes direction when moving between media with different optical densities.

18. Determine the angle of refraction if $n_1=1.5$, $n_2=1.0$, and $\theta_1=45^\text{o}$.

    $\theta_2 = \text{sin}^{-1}(1.5 \times \text{sin}(45^\text{o}))$. Light exits glass into air, bending away from normal.

19. What is the effect of refraction on the shape of a swimming pool viewed from above?

    The pool appears shallower due to refraction. Refraction makes objects appear closer to surface.

20. How does temperature affect the refractive index of gases?

    Refractive index decreases with increasing temperature. Higher temperature decreases gas density, reducing $n$.

21. Identify the unit of the index of refraction.

    The index of refraction is dimensionless. It's a ratio of speeds, so no units.

22. State the relationship between frequency and speed of light in a medium.

    Frequency remains constant; speed changes. Energy conservation requires frequency to remain constant.

23. What is total internal reflection?

    When light reflects entirely back into a medium beyond the critical angle. Occurs when angle exceeds critical angle in denser medium.

24. What does the index of refraction represent?

    The index of refraction measures how much light slows in a medium. Compares light speed in a medium to speed in vacuum ($c$).

25. What is the critical angle?

    The angle of incidence at which light is refracted along the boundary. Beyond this angle, total internal reflection occurs instead.

26. Identify the effect of frequency on refraction.

    Higher frequency light refracts more than lower frequency. Higher frequency means higher energy and greater refraction.

27. What is the formula for the speed of light in a medium?

    $v = \frac{c}{n}$. Relates medium speed to vacuum speed through refractive index.

28. State the effect of increasing wavelength on the angle of refraction.

    Increasing wavelength decreases the angle of refraction. Longer wavelengths have lower refractive indices.

29. What happens to the direction of light when it passes through a rectangular glass block?

    The light exits parallel to its original path. Parallel entry and exit with lateral displacement only.

30. State Snell's Law formula.

    $n_1 \times \text{sin}(\theta_1) = n_2 \times \text{sin}(\theta_2)$. Relates incident and refracted angles through refractive indices.

31. What occurs when light passes from a more dense to a less dense medium?

    Light bends away from the normal. Lower optical density causes light to bend away from the normal.

32. Find the angle of refraction when light enters glass ($n=1.5$) from air at $30^\text{o}$.

    $\theta_2 = \text{sin}^{-1}(\frac{\text{sin}(30^\text{o})}{1.5})$. Applies Snell's law with $n_1 = 1$ and $n_2 = 1.5$.

33. Calculate the refractive index of a medium if $c=3\times10^8 \text{m/s}$ and $v=2\times10^8 \text{m/s}$.

    $n = \frac{3\times10^8}{2\times10^8} = 1.5$. Direct calculation using $n = \frac{c}{v}$.

34. Identify the cause of a mirage.

    A mirage is caused by refraction of light in varying air densities. Temperature gradients create layers with different refractive indices.

35. What is the phenomenon when the sun appears before its rise due to refraction?

    This phenomenon is called atmospheric refraction. Light bends through varying atmospheric density layers.

36. Calculate the speed of light in water ($n=1.33$).

    $v = \frac{c}{1.33}$. Light speed equals vacuum speed divided by refractive index.

37. What is dispersion?

    The separation of light into colors by refraction. Different wavelengths refract by different amounts.

38. What is the effect of refraction on an image through a lens?

    The image can be magnified or minimized. Refraction at curved surfaces creates optical magnification effects.

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