AP Physics 2:: Optics

What is the LAW OF REFLECTION, and what does it state about the relationship between the ANGLE OF INCIDENCE and the ANGLE OF REFLECTION for light bouncing off a flat, smooth surface?

- **A)** The law of reflection states that the angle of incidence and angle of reflection are always DIFFERENT, with no actual fixed relationship between them
- **B)** This law has no actual mathematical relationship between the angle of incidence and the angle of reflection
- **C)** Angles for reflection are measured from the reflecting SURFACE itself, rather than from the NORMAL (perpendicular) line
- **D)** The law of reflection states that the ANGLE OF INCIDENCE EQUALS the ANGLE OF REFLECTION, with BOTH angles measured from the NORMAL (a line perpendicular to the reflecting surface) -- light bounces off a mirror at the SAME angle it arrived at

What is REFRACTION, and what PHYSICAL PROPERTY of light changes as it PASSES from one transparent medium (like air) into another (like water or glass), causing the light ray to BEND at the boundary?

- **A)** Refraction occurs because light's COLOR changes when passing between media, with no actual relationship to a change in light's speed
- **B)** This concept has no actual relationship between a change in light's speed and the bending observed during refraction
- **C)** Refraction only occurs when light passes from a denser medium to a LESS dense medium, with no actual bending occurring in the opposite direction
- **D)** Refraction is the BENDING of light as it passes between two different transparent media; this bending occurs because light's SPEED changes when it enters a different medium (light travels at different speeds in different materials)

What is the INDEX OF REFRACTION of a material, and what is its mathematical FORMULA in terms of the SPEED OF LIGHT in a vacuum compared to the speed of light WITHIN that material?

- **A)** The index of refraction (n) is the RATIO of the speed of light in a VACUUM to the speed of light WITHIN a given material; n = c/v, where c is the speed of light in vacuum and v is light's speed in the material -- a HIGHER index of refraction means light travels MORE SLOWLY in that material
- **B)** The index of refraction is calculated as n = v/c (material speed divided by vacuum speed), rather than vacuum speed divided by material speed
- **C)** A HIGHER index of refraction means light travels FASTER in that material, the reverse of the actual relationship
- **D)** This concept has no actual mathematical relationship between the index of refraction and the speed of light in vacuum versus within a material

What is SNELL'S LAW, and what is its mathematical FORMULA relating the ANGLES of incidence and refraction to the INDICES OF REFRACTION of the two media involved?

- **A)** Snell's Law states that n1*theta1 = n2*theta2 (directly multiplying index by angle, without using sine), rather than the correct sine-based relationship
- **B)** Snell's Law states that n1*sin(theta1) = n2*sin(theta2), where n1 and theta1 are the index of refraction and angle in the FIRST medium, and n2 and theta2 are the corresponding values in the SECOND medium -- this equation quantitatively predicts how much a light ray bends when crossing between two media
- **C)** This law has no actual mathematical relationship between the indices of refraction and angles of incidence/refraction for two media
- **D)** Snell's Law applies only when both media have the IDENTICAL index of refraction, making it inapplicable to situations involving actual refraction/bending

When light travels from a medium with a LOWER index of refraction (like air) into a medium with a HIGHER index of refraction (like glass), does the light ray bend TOWARD or AWAY FROM the normal line, based on Snell's Law?

- **A)** Light bends TOWARD the normal when entering a medium with a HIGHER index of refraction (moving into a 'denser' optical medium slows the light down and decreases the angle from the normal, consistent with n1*sin(theta1)=n2*sin(theta2) requiring a SMALLER angle when n2 is LARGER)
- **B)** Light bends AWAY FROM the normal when entering a medium with a higher index of refraction, the reverse of the actual bending direction predicted by Snell's Law
- **C)** This concept has no actual relationship between the relative index of refraction of two media and the direction light bends at their boundary
- **D)** Light does not bend at all when passing into a medium with a different index of refraction, contradicting the basic definition of refraction

What is TOTAL INTERNAL REFLECTION, and under what CONDITION (regarding the angle of incidence and the CRITICAL ANGLE) does this phenomenon occur when light travels from a HIGHER-index medium toward a LOWER-index medium?

- **A)** This concept has no actual relationship between the angle of incidence, the critical angle, and whether total internal reflection occurs
- **B)** Total internal reflection occurs only when light travels from a LOWER-index to a HIGHER-index medium, the reverse of the actual direction required for this phenomenon
- **C)** Total internal reflection occurs at ALL angles of incidence, regardless of any critical angle threshold
- **D)** Total internal reflection occurs when light traveling from a higher-index to a lower-index medium strikes the boundary at an angle GREATER than the CRITICAL ANGLE -- instead of refracting through the boundary, ALL of the light is REFLECTED back into the original, higher-index medium

What is the mathematical FORMULA for the CRITICAL ANGLE (the specific angle of incidence at which total internal reflection begins), in terms of the two media's indices of refraction?

- **A)** The critical angle depends only on the index of the ORIGINAL medium, with no actual dependence on the second medium's index
- **B)** sin(theta_critical) = n1/n2 (inverting the correct ratio), rather than n2/n1
- **C)** sin(theta_critical) = n2/n1, where n1 is the index of the ORIGINAL (higher-index) medium and n2 is the index of the medium light is attempting to enter (LOWER-index) -- this formula is derived by setting the refraction angle in Snell's Law to exactly 90 degrees
- **D)** This concept has no actual mathematical relationship between the critical angle and the indices of refraction of the two media involved

What is a real-world PRACTICAL application of total internal reflection in explaining how FIBER OPTIC CABLES can transmit light (and encoded data) over LONG DISTANCES with minimal signal loss, by repeatedly reflecting light WITHIN the fiber's core?

- **A)** Total internal reflection in fiber optics only works for SHORT distances, making it unsuitable for long-distance data transmission
- **B)** Fiber optic cables have no actual relationship to total internal reflection or to how light travels through the fiber's core
- **C)** Fiber optic cables are designed so that light entering the fiber's core strikes the core-cladding boundary at an angle GREATER than the critical angle, causing TOTAL INTERNAL REFLECTION -- the light bounces repeatedly along the fiber's length WITHOUT escaping or significantly weakening, allowing efficient long-distance signal transmission
- **D)** Fiber optic cables work by allowing light to continuously REFRACT OUT of the fiber at each boundary encounter, rather than being reflected back inside