A certain luminous surface obeys Lambert's law. Its luminance is equal to `L`. Find:
(a) the luminous flux emitted by a element `DeltaS` of this surface into a cone whose axis is normal to the given element and whose aperture angle is equal to `theta`,
(b) the luminosity of such a source.

A Lamber source has a luminance L. Find: (a) the luminuous flux emitted by an element DeltaS of this surface into the forward cone along the normal to DeltaS and of semivertical angle theta , (b) the luminosiy of such a source.

A Lambert source has the from of an infinite plane. Its luminance is equal to L . Find the illuminance of an area element oriented parallel to the given source.

Determine the luminosity of a surface whose luminance depends on direction as L = L_(0) cos theta , where theta is the angle between the radiation direction and the normal to the surface.

The magentic induction in vacumm at a plaen surface of a magentic is equal to B and the vector B forms an angle theta with the normal n of the surface (Fig). The permeability of the magnetic is equal to mu . Find: (a) the flux of the vector H through the spherical surface S of radius R , whose centre lies on the surface of the magentic, (b) the circulation of the vector B around the square path I' widh side l located as shwon in the fig.

The magnetic induction in vacumm at a plane surface of a uniform istropic magnetic is equal to B , the vector B forming an angle alpha with the normal of the surface. The permeability of th emagnetic is equal to mu . Find the magnitic of the magnetic induction B" in the magnetic in the vicinity of its surface.

A disc A of mass m sliding over a smooth horizontal surface with velocity v experiences a perfectly elastic collision with a smooth stationary wall at a point O (figure). The angle between the motion direction of the disc and the normal of the wall is equal to alpha . Find: (a) the points relative to which the angular momentum M of the disc remains constant in this process, (b) the magnitude of the increment of the vector of the disc's angular momentum relative to the point O^' which is located in the plane of the disc's motion at the distance l from the point O.

A particle is projected from point P with velocity 5sqrt(2)m//s perpendicular to the surface of a hollow right angle cone whose axis is vertical. It collides at Q normally. Find the time of the flight of the particle.

A point source emitting uniformly in all directions is placed above a table top at a distance of 0.50 m from it. The luminous flux of the source is 1570 lumen. Find the illuminance at a small surface area of the table to a.directly below the source and b. at as distance of 0.80 m from the source.

A point source emitting uniformly in all directions is placed above a table top at a distance of 0.50 m from it. The luminous flux of the source is 1570 lumen. Find the illuminance at a small surface area of the table to a.directly below the source and b. at as distance of 0.80 m from the source.

A point source emitting uniformly in all directions is placed above a table top at a distance of 0.50 m from it. The luminous flux of the source is 500 lumen. Find the illuminance at a small surface area of the table to a.directly below the source and b. at as distance of 0.80 m from the source.