Two sources of light of equal illuminating power are placed at a distance of 1.2m from one another. Where should a screen be placed between the two sources so that intensity of illumination due to one of the sources is 4 times due to that of the other.

Two sources of lights of illuminating powers in the ratio1:2 are placed on a line 2 meter apart. At what point is the spae between them equally illuminated?

At what distance form a light source of 64 cd, will the intensity of illumination because 4 flux ?

Two light sources of intensities 8 cd and 12 cd are placed on the same side of a photometer screen at a distance of 40 cm from it. Where should a 80 cd source be placed to balance the illuminance ?

Two point light sources are 24 cm apart. Where should a convex lens of focal length 9 cm be put in between them from one source so that the images of both the sources are formed at the same place

A screen is placed at a distance of 1m from a point of source of light . What will be the effect on the intensity (I) of light observed on the screen , if the screen is kept at 150 cm from the same point source ?

Two sources of light are at distance 0.6m and 0.9m on either side of a screen for matching. When a glass plate is introduced between the weaker source and the screen, the other source has to be moved 0.2m farther to match the illumination. Calculate the percentage of the light stopped by the glass plate introduced.

A monochromatic point source (S_(1)) is at a distance d from a screen. Another identical source (S_(2)) is at a large distance from the screen. The two sources are on a line which is perpendicular to the screen. Sources are coherent. What is the shape of interference fringes on the screen? (b) Three identical coherent sources are placed on a straight line with two neighbouring ones separated by a distance "d = 0.06 mm" . The sources produce monochromatic light of wavelength lambda" = 550.4 nm" . A line AB is located at a distance D = 2.50 m from the sources and is perpendicular to line joining the three sources. Intensity of light at P with any one of the sources switched on is I_(o) . Find the intensity when all three sources are switched on. Distance of point P from O is "y = 1.72 cm (see figure)"

A photo cell is receiving light from a source placed at a distance of 1 m . If the same source is to be placed at a distance of 2 m , then the ejected electron