Physics Flashcards

When light travels from a denser medium to a rarer medium at an angle greater than the critical angle, what phenomenon occurs?

Answer: Total internal reflection

Total internal reflection occurs when light strikes the interface at an angle exceeding the critical angle while traveling from denser to rarer medium.

A convex lens of focal length 20 cm forms a real image of an object placed 30 cm from the lens. The image distance is:

Answer: 60 cm

Using lens formula 1/v − 1/u = 1/f: 1/v = 1/20 + 1/(−30) = 1/60, so v = 60 cm.

In Young's double slit experiment, if the distance between the slits is halved and the distance to the screen is doubled, the fringe width becomes:

Answer: 4 times

Fringe width β = λD/d; when d is halved and D is doubled, β becomes 4 times the original.

The energy of a photon with wavelength λ is E. If the wavelength is doubled, the energy becomes:

Answer: E/2

Since E = hc/λ, doubling wavelength halves the energy to E/2.

Which colour of visible light has the highest frequency?

Answer: Violet

Violet light has the shortest wavelength (~400 nm) in the visible spectrum and therefore the highest frequency.

The phenomenon responsible for the blue colour of the sky is:

Answer: Rayleigh scattering

Rayleigh scattering causes molecules to scatter blue light (shorter wavelength) much more strongly than red, making the sky appear blue.

A ray of light passes through an equilateral prism at minimum deviation. The angle of incidence is approximately:

Answer: 60°

For an equilateral prism (A = 60°) at minimum deviation, the ray passes symmetrically and the angle of incidence equals approximately 60°.