Saved Bookmarks
| 1. |
A nail is fixed up perpendicularly at the centre of a circular wooden plate. Keeping the nail at bottom, the circular plate is made of float in water. What should be the maximum ratio of the radius of the plate and length of the nail so that the nail wil be out of vision? Refractive index of water = (4)/(3). |
|
Answer» Solution :AB is the circular wooden plate and CD is the nail. Suppose, RADIUS of the plate = r and the length of the nail = h [Fig. 2.30]. Since the nail is not seen from air, the angle of incidence of the RAY DA will be GREATER than `theta_(c)` and the ray will be totally reflected. `"We know", sintheta_(c) = (1)/(a^(mu)w) = (3)/(4)` `therefore "" costheta_(c) = sqrt(1-(9)/(16)) = sqrt(7)/(4) and tantheta_(c) = ((3)/(4))/((sqrt7)/(4)) = (3)/(sqrt7)` `or, "" (r)/(h) = (3)/(sqrt7)` This is the required ratio. 
|
|