Light rays from a source are incident on a glass prism of index of refraction μ and angle of prism α. At near normal incidence, the angle of deviation of the emerging rays is
Variation of angle of deviation δ versus angle of incidence for a prism is given the figure. The value of refractive index of prism :
In the displacement method, a convex lens is placed in between an object and a screen. If magnification in the two positions are \(m_1\) and \(m_2\) (\(m_1 > m_2\)) and the distance between two positions of the lens is x, the focal length of the lens is
In displacement method, \(m_1 = \frac{v_1}{u_1}\) and \(m_2 = \frac{v_2}{u_2} = \frac{u_1}{v_1}\). Since the distance between two positions is \(x = v_1 - u_1\), we obtain \(m_1 - m_2 = \frac{x}{f}\), hence \(f = \frac{x}{m_1-m_2}\).