Ray Optics and ...

A $$60\ watt$$ bulb is hung over the center of a table $$4m \times 4\ m$$ at a height of $$3\ m$$. The ratio of the intensities of illumination at a point on the centre of the edge an don the corner of the table is

At sun rise of sunset, the sun looks more red than at mid-day because

Refractive index of glass is $$\dfrac {3}{2}$$ and refractive index of water is $$\dfrac {4}{3}$$. If the speed of light in glass is $$2.00\times 10^8\ m/s$$ , the speed in water will be

The relation between the linear magnification $$m,$$ the object distance $$u$$ and the focal length $$f$$ is 

Each quarter of a vessel of depth $$H$$ is filed with liquids of the refractive indices, $$n_1, n_2, n_3$$ and $$n_4$$ from the bottom respectively. The apparent  depth of the vessel when looked normally is

A convex lens is used to form real image of an object on a screen. It is observed that even when the positions of the object and that screen are fixed are two position of the lens to form real images. If the heights of the images are $$4\ cm$$ and $$9\ cm$$ respectively the height of the object is

When a ray of light passes through the second optical medium with a change in the angle, the phenomenon is known as:

The length of a simple astronomical telescope is equal to:

The sky would appear red instead of blue if

Two point light source 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.