For every value of $$x$$, the function $$f(x)=\frac{1}{a^x}, a>$$ 0 is,

If a die is thrown at random, then the expectation of the number on it is

A body slides down a smooth inclined plane having angle $$\theta$$ and reaches the bottom with velocity $$v$$. If a body is a sphere, then its linear velocity at the bottom of the plane is

A light wave of wavelength $$\lambda$$ is incident on a slit of width $$d$$. The resulting diffraction pattern is observed on a screen at a distance $$D$$. If linear width of the principal maxima is equal to the width of the slit, then the distance $$D$$ is