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A red LED emits light at 0.1 watt uniformly around it. The amplitude of the electric field of the light at a distance of 1 m from the diode is
What are the essential properties a medium must possess for the propagation of mechanical waves?
A radiation energy 'E' falls normally on a perfectly reflecting surface. The momentum transferred to the surface is PE/C, then P is 
In the arrangement shown a point source of light S is placed 60 cm to the left of a convex lens of focal length 30 cm and 2 cm above the common principal axis of the convex lens and a convex mirror of focal length 10 cm. Consider optic centre of the lens to be the origin, the xcoordinate of the final image of the source S for the viewer left to the lens is equal to (– K) cm. Calculate the value of K.
An isotropic point source of light is kept at distance of 60 cm from a screen, the intensity of light obtained on center is I_{1}. Now a lens of focal length 20 cm is introduced at exactly midway between source and screen and intensity obtained is I_{2}. Find I_{2}/8I_{1}.
A wave of frequency 100 Hz travels along a string towards its fixed end. When this wave travels back, after reflection, a node is formed at a distance of 10 cm from the fixed end. The speed of the wave (incident and reflected) is :
357 docs148 tests

357 docs148 tests
