An observer looks at an kept at an distance 30cm in air.If an rectangular glass plate is placed between the observer and the object with its thickness along the line of observations, the object appears to the observer to be at a distance 25cm Find the thickness of glass plate. Position of the glass plate is now shifted (i) from object towards observers (ii) from observer towards the object. How does it change the apparent position of the object as seen by the observer?

An observer looks at an kept at an distance 30cm in air.If an rectangu

1.	An observer looks at an kept at an distance 30cm in air.If an rectangular glass plate is placed between the observer and the object with its thickness along the line of observations, the object appears to the observer to be at a distance 25cm Find the thickness of glass plate. Position of the glass plate is now shifted (i) from object towards observers (ii) from observer towards the object. How does it change the apparent position of the object as seen by the observer?
Answer» Solution :As a glass plate is placed between the observer and the object, the object appears to be at a distance 25CM instead of 30CM, IT IMPLIES the normal shift due to refraction at the glass plate is 30-25=5cm. Normal shift `=t(1-1/mu)` Hence `t(t-1/mu)=5 t(t-1/1.5)=5, therefore t=15cm` Since the plate has given values of refractive index (1.5) and THICKNESS (15cm) if its position is shifted if, will not change the values of normal shift `t(I-1/mu)` It implies that the object will appear to be at the same distance 25cm and its apparent position remains the same.