why are totally reflecting prisms preferred to a plane mirror even though plane mirrors are cheaper?

Answer 1

When ever there is reflection on any surface there is refraction also beneath the surface.

The energy of the incident beam is partially reflected and partially absorbed.

Even a good mirror reflects nearly 80%of the incident light only.

At normal incidence (Incident perpendicular to the surface) there is no reflection and all the light rays pass through the surface.

When a ray passes through a denser medium and tries to enter a rarer medium and if the angle of incidence is more than the critical angle, we say there is total internal reflection.

The total here implies that there is no refraction at all. The entire ray is refracted.

Therefore when we use totally reflecting prisms, there is no energy is lost due to normal incidence from air to glass and there is TOTAL (no partial refraction) reflection inside the prism.

Thus the light is reflected almost 100% in totally reflecting prisms and hence they are preferred even though in costs high.

Answer 2

Reflecting Prism

Answer 3

Totally reflecting prisms are preferred as with a plane mirror you get a double reflection (one off the first glass surface and then one off the back silvering of the mirror), while totally reflecting prisms dont as their first surface reflects all the light

Answer 4

Prisms have higher reflectivity and can be more precisely made than mirrors. Next best are dielectric mirrors, made up of layers of interference coating. Even the best metal films introduce a little bit of scatter and absorb a few percent of the light. Dielectric films can have 99% reflectivity and very low scatter; prisms essentially have 100% reflectivity, losing only a fraction of a percent of the light to absorption.

Answer 5

They do not absorb any ray during the time of reflection thus, image is brighter. they have a high refracting index and so they reflect more. This is why diamond shines more than a mirror.