1. For achromatic combination of lenses, if we use two lenses of focal length f' and f1 dipersive power to ω and ω' respectively, then
2. ar point of a myopic eye is 40 cm. The dioptic power of a corrective lens is:
3. Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact. The effective power of the combination is:
4. A blue cross on the white background is illuminated with white light and is observed through red filter. What is seen?
5. The angle of deviation for a prism is greatest for:
6. A double convex air bubble in water behaves as: