Task 3.5
A physical pendulum is a thin rod suspended at one of its ends. When
What length of the rod does the oscillation period of this pendulum be 1 s?
Task 3.15
A plane electromagnetic wave propagates in the medium (? = 3,? = 1). Amplitude of tension
The magnetic field of the wave is 0.5 A / m. On its way it is perpendicular to a direction of distribution
There is an absorbing surface, which has the form of a circle with a radius of 0.1 m. What is the energy
Absorption by this surface in a time t = 30 s? The period of the wave is T << t.

Task 3.25
To eliminate the reflection of light on the surface of the glass lens, a film of the substance with
The index of refraction is 1.3 smaller than that of glass. At what is the smallest thickness of this film
Reflection of light with a wavelength of 0.48 μm will not be observed if the angle of incidence of the rays is 30 °?
Task 3.35
The constant of the diffraction grating is 5 μm. Determine the largest order of the spectrum, the total number
Main maxima in the diffraction pattern and the diffraction angle in the fourth-order spectrum at
Normal incidence of monochromatic light with a wavelength of 0.625 μm?

Task 3.45
Natural light falls on the surface of the dielectric at an angle of total polarization. Power
The polarization of the refracted beam is 0.09. Find the reflection coefficient of light.

Task 3.55
A beam of relativistic electrons moves in glycerin. Will there be a Cherenkov glow,
If the kinetic energy of the electrons is 0.34 MeV?

Task 3.65
Calculate the temperature of the Earth's surface, assuming its constant, under the assumption that the Earth as
The black body radiates as much energy as it receives from the Sun. The intensity of the solar
Radiation near the Earth is assumed equal to 1.37 kW / m2.
Task 3.75
Find the magnitude of the delayed potential difference for photoelectrons emitted at illumination
Cesium electrode with ultraviolet rays with a wavelength of 0.3 μm.