Physics: Optics and Waves Flashcards

A concave mirror has a radius of curvature of 30 cm. An object is placed 45 cm in front of it. The image distance is:

Answer: 22.5 cm in front

Focal length = R/2 = 15 cm; 1/f = 1/do + 1/di → 1/15 = 1/45 + 1/di → di = 22.5 cm in front (real image).

In Young's double-slit experiment, if the slit separation is doubled while keeping all else constant, the fringe spacing:

Answer: Is halved

Fringe spacing Δy = λL/d, so doubling slit separation d halves the fringe spacing.

The Doppler effect for sound predicts that as a source moves toward a stationary observer, the observed frequency:

Answer: Increases

As the source approaches, wavefronts are compressed, increasing the observed frequency (blue shift for sound).

Which color of visible light has the greatest energy per photon?

Answer: Violet

Photon energy E = hf = hc/λ; violet light has the shortest wavelength (~400 nm) and thus the highest frequency and energy.

A light ray travels from water (n = 1.33) into glass (n = 1.52). The ray bends:

Answer: Toward the normal

When light enters a denser medium (higher n), it bends toward the normal per Snell's law.

Standing waves in a string fixed at both ends have nodes at:

Answer: Both endpoints and at integer multiples of half-wavelengths

Fixed ends are always nodes; additional nodes occur at every half-wavelength along the string's length.

The index of refraction of a material is defined as:

Answer: The ratio of speed in vacuum to speed in the material

Index of refraction n = c/v, where c is the speed of light in vacuum and v is its speed in the medium.