Waves and Optics Flashcards (Video Notes)

A comprehensive set of Q&A-style flashcards covering waves, their properties, and fundamental optics concepts from the lecture notes.

What do waves transfer?

Energy (not matter).

What is the key difference between mechanical waves and electromagnetic waves?

Mechanical waves require a medium to propagate; electromagnetic waves can travel through vacuum.

How do transverse waves differ from longitudinal waves in terms of particle displacement?

Transverse waves have particle displacement perpendicular to the direction of travel; longitudinal waves have displacement parallel to the direction of travel (with compressions and rarefactions).

Give examples of transverse waves and longitudinal waves.

Transverse: waves on a string, surface water waves, electromagnetic waves. Longitudinal: sound waves in air, compression waves in springs.

What term describes the maximum displacement of a point on a wave from its rest position?

Amplitude.

What term describes the region where particles are crowded together in a longitudinal wave?

Compression.

What term describes the region where particles are spread apart in a longitudinal wave?

Rarefaction.

What term describes the highest point of a transverse wave?

Crest.

What term describes the lowest point of a transverse wave?

Trough.

What term refers to how far a point on the medium has moved from equilibrium?

Displacement.

What term is used for the time for one complete cycle of the wave?

Period.

What term means the number of cycles per second?

Frequency.

What term is the distance between corresponding points on adjacent cycles?

Wavelength.

What term describes how fast the wave travels?

Velocity.

How can you determine amplitude, period, frequency, and wavelength from a transverse-wave graph?

Amplitude: maximum vertical displacement from equilibrium. Period: time between successive identical points (e.g., crests). Frequency: 1/Period. Wavelength: distance between consecutive crests (or troughs) in space.

What are the two fundamental equations relating wavelength, frequency, period, and velocity?

v = f λ and f = 1/T (where T is the period).

List the regions of the electromagnetic spectrum.

Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

How should you order electromagnetic-spectrum regions by wavelength, frequency, and energy?

By wavelength: longest to shortest (radio → microwaves → infrared → visible → ultraviolet → X‑rays → gamma). By frequency: inverse order (gamma → X‑rays → visible → infrared → microwaves → radio). Energy increases with frequency.

What kind of light does the Sun emit?

White light (a mixture of colors).

What is dispersion in optics?

The separation of light into component colors due to wavelength-dependent refractive index (different colors refract differently; colour ∝ wavelength/frequency).

What are the primary colors of light?

Red, Green, Blue.

What are the secondary colors of light?

Cyan, Magenta, Yellow.

What is colour addition?

Adding light colors (RGB) to produce white; e.g., Red + Green + Blue ≈ white.

What is colour subtraction?

Subtracting wavelengths using pigments or filters; e.g., cyan, magenta, yellow subtract light to produce other colors.

What are reflection, refraction, interference, and diffraction?

Reflection: light bounces off a surface; Refraction: light bends at a boundary due to speed change; Interference: waves superpose to give constructive or destructive patterns; Diffraction: bending of waves around obstacles or through openings.

What phenomena are typically associated with reflection?

Light follows the law of reflection; angle of incidence equals angle of reflection; image formation in mirrors.

What is the Law of Reflection?

Angle of incidence equals angle of reflection (θi = θr).

What is the refractive index?

n = c/v, the ratio of the speed of light in vacuum to its speed in the medium.

What is total internal reflection?

When light attempts to move from a denser to a rarer medium at an angle greater than the critical angle, all light is reflected back into the denser medium.

What is the critical angle?

The angle of incidence in the denser medium for which the refracted ray travels along the boundary (sin θc = n2/n1, with n1 > n2).

What is Snell's Law?

n1 sin i = n2 sin r (relationship between incident and refracted angles at a boundary).

What do ray diagrams illustrate in reflection and refraction by concave and convex mirrors and lenses?

The paths of light rays and the formation of images using these optical components.

What is a common lens/mirror formula used for single optical component problems?

1/f = 1/do + 1/di (and magnification m = -di/do); these relate focal length, object distance, and image distance.

What happens to a light ray when it moves from a denser to a rarer medium and its incidence angle is above the critical angle?

Total internal reflection occurs; the ray is completely reflected within the denser medium.

What equation relates the speed of light in a medium to its refractive index and the speed of light in vacuum?

v = c / n (or n = c / v).