Physics II Module of the MCAT Self Prep eCourse: Lesson 8: Reflection (Pro)

Compare specular reflection to diffuse reflection

*Specular reflection* is defined as light reflected from a smooth surface at a definite angle. Here, were are only talking about the light that is *reflected* *Diffuse reflection* is produced by rough surfaces that tend to reflect light in all directions. Here, we are talking about light that is being *absorbed and reflected.* So, this explains an apple appearing red. ★ There are far more occurrences of diffuse reflection than specular reflection in our everyday environment.

What are diopters in SI units?

1/m

(*K*) Total internal reflection occurs when light travels from a medium of __________ index of refraction to one of ____________ index of refraction

High to low

At the critical angle, does the light ray emerge from the first medium?

It's travels at a 90 degree angle so it doesn't look like it is emerging; however, it is not reflecting yet either

(*K*) Which of the following will not result in the splitting of white light into its component colors? A. Dispersion through a prism B. Diffraction through a grating C. Refraction within a thin film D. Reflection from an ideal convex mirror

Reflection from an ideal convex mirror Explanation: A mirror with significant aberration could lead to a separation of light into its component colors, but we are told this is an ideal mirror. All the other options result in light splitting into component colors.

Which lens would have greater power, one with a shorter focal length or one with a longer focal length?

Shorter Explanation: top one bends light more

What is the critical angle (θc)?

an angle of *incidence* where the resulting refracted ray is refracted 90°

For a convex mirror, the center of curvature and the radius of curvature are ___________ the mirror.

behind

For concave mirrors, as the object gets closer to the focal point, (but still outside the focal point), the resulting image gets ____________.

bigger (enlarged) and *image* moves away from the focal point

What is the relationship between radius of curvature and focal length?

f = R/2

When light travels through a homogenous medium, how does it travel?

in a straight line *rectilinear propagation*

For a concave mirror, the center of curvature and the radius of curvature are ___________ the mirror.

in front of

For most materials, the smaller the wavelength (λ) of light, the ______________ the index of refraction (n).

larger

How does rectilinear propagation explain shadows?

light radiates out from a source in all directions but since it travels in straight lines, it cannot bend around an object, so a shadow is created in the areas where light cannot get to

Smaller wavelength light bends ____________ than larger wavelength light in most materials.

more thus the angle will be smaller!

(*K*) All angles in optics are measured from the _____________.

normal drawn perpendicular to the boundary of a medium

When something is reflected in a plane mirror, its image in the mirror is ____________.

reversed

For concave mirrors, as the object gets further away from the focal point, the resulting image gets ____________.

smaller (reduced) and *image* approaches the focal

When the critical angle is exceeded, what happens?

total internal reflection

True or False: Plane mirrors always create virtual images.

true Explanation: a real image only forms if light actually converges at the position of the image, and with plane mirrors, there is neither convergence nor divergence. It's just simple reflection

(*K*) True or False: Plane mirrors cause neither convergence nor divergence of reflected light rays.

true Explanation: parallel incident rays remain parallel after reflection from a plane mirror.

(*K*) Monochromatic red light is allowed to pass between two different media. If the incident angle in medium 1 is 30° and the incident angle in medium 2 is 45°, what is the relationship between the speed of light in medium 2 compared to that in medium 1? A. v₂ = v₁√2 B. v₂√2 = v₁ C. v₂ = v₁√3 D. v₂√3 = v₁

v₂ = v₁√2

What is total internal reflection?

when light travels from a medium of higher refraction index to one of lighter refraction index, at a certain incident angle (θc), the refracted ray will be 90°. *When this angle is exceeded, total internal reflection occurs*

What is the center of curvature?

would be the center of the spherically-shaped mirror if it were a complete sphere, so it's a *point* whereas the radius of curvature is the *distance* from that point to the vertex of the mirror

What is the modified version of Snell's Law using the critical angle?

θ₂ is 90° and since sin(90°) = 1, the formula can be simplified.

(*K*) Imagine that a beam of monochromatic light originates in air and is allowed to shine upon the flat surface of a piece of glass at an angle of 60° with the normal. The reflected and refracted beams are perpendicular to each other. What is the index of refraction of the glass? A. √3/3 B. 1 C. 2 D. √3

√3