An electric bulb is hanging over a table at a height of 1 m above it. The illuminance on the table directly below the bulb is 40 lux. The illuminance at a point on the table 1 m away from the first point will be about
Given:
Distance of bulb from table, PQ = 1 m
Distance of point from table, QR = 1 m
Luminosity, I0 = 40 lux
Calculation:
The position of the bulb is at the point P and position of the point is at R. As, both the sides of the triangle is 1 m. Thus, given triangle is isosceles triangle and the angle θ = 450.
The length of the side PR is, 
The illuminance is given as,
E = 14 lux
So, option B is correct.
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