Physics Answers

Find the ratio of the optical power (force) of the lenses made from glass and

diamond with the same radius of curvature. The index of refraction of glass is n_g = 1.5,

the index of refraction of diamond is n_d = 2.42 and the index of refraction of air is n = 1.

Some body of the height 2cm is at the distance of 15cm from the diverging lens

with the focal length (distance) 0.1m. Where will be the image of the body? What size will

be the image of the body?

Find the maximum speed v_max of the photoelectrons leaving the surface of silver

under the influence of the ultraviolet radiation of the wave length λ = 0.155μm. The work

function of silver is A = 4.7 eV.

Problem: The total luminous flux falling onto the floor and the walls from the electrical

bulb that is fixed to the ceiling of the room is 314 lm. Find the luminous intensity of the

bulb if the luminous flux is the same in all directions.

The beam of a natural light falls onto the surface of the glass plate that is situated

in the liquid. The angle between the incident light and the reflected light is φ. Find the

formula determining the index of refraction n₂ of the glass plate if the reflected light is

fully polarized and the index of refraction n₁ of the liquid is known.

Problem: Find the minimal resolving power of the diffraction grating (lattice) if it enables

us to resolve the two spectral lines of potassium (λ1 = 578 nm and λ2 = 580 nm). How

many minimal numbers of strokes (slits) (N) should have this grating that the resolving is

possible in the spectrum of the second order.

The beam of parallel light rays falls onto the surface of water under the angle

60°

. The width of the beam in the air is 10 cm. Find the width of the beam in the water.

The parallel beam of light from a monochromatic source (λ = 0.6μm) falls onto

the slit of the width a = 0.1 mm. Determine the breadth (width) l of the central maximum

in the diffraction pattern that is projected onto the screen by the lens situated directly behind

the slit, i.e. the lens is between the slit and the screen. The screen is at the distance L = 1m

from the lens.

Determine the total luminous flux emitted by the source if the illumination is

15 lx at the distance 2 m from that source. The luminous intensity is equal in all directions.

Determine the force of gravity of the meteorites when it reaches one quarter of its distance from the center of Earth if the force of gravity of a meteorite approaching Earth is 50,000 N.