A lamp is hanging along the axis of a circular table of radius r. at what height should the lamp be placed above the table so that the intensity of illumination at the edge of the table is `(1)/(8)` of that at its centre ?

A small source of light is to be suspended directly above the centre of a circular table of radius R . What should be the height of the light source above the table so that the intensity of light is maximum at the edges of the table compared to any other height of the source

At what height should a lamp be hung above the centre of a round table of radius R to otain the maximum illumination at its edges?

If anelectric lamp be suspended at a height h from a circular table of radius r, prove that the intensity of illumination at thecentre of the table is (1+(r^(2))/(h^(2)))^(3//2) times that at the edge of the table.

An electric lamp hangs 3 m above one end of a table, which is 4 m long. Compare the intensity of illumination at the two ends of the table.

An electric bulb is hanging above the centre of a circular table of radiys 3m at a height of 3m from the its centre. Find the ratio of illuminance at the centre and at a point on the edge of the table.

A lamp hanging 4 metres above the table is lowered by 1 metre. Illumination on the table

A lamp rated at 100 cd hangs over the middle of a round table with diameter 3 m at a height of 2 m . It is replaced by a lamp of 25 cd and the distance to the table is changed so that the illumination at the centre of the table remains as before. The illumination at edge of the table becomes X times the original. Then X is