Geometrical OpticsHard
Question
A converging beam of rays is incident on a diverging lens. Having passed through the lens the ray intersect at a point 15 cm from the lens on the opposite side. If the lens is removed the point where the rays meet will move 5 cm closer to the lens. The focal length of the lens is
Options
A.5 cm
B.- 10 cm
C.20 cm
D.- 30 cm
Solution
Here, v = + 15 cm, u = + (15 - 5) = + 10 cm
According to lens formula
⇒ 
f = - 30 cm.
According to lens formula
⇒ f = - 30 cm.
Create a free account to view solution
View Solution FreeMore Geometrical Optics Questions
The length of astronomical telescope is 15 cm and has magnifying power 4 for normal adjustment. Focal length of the lens...A thin prism having refracting angle 10o is made of glass of refractive index 1.42. This prism is combined with another ...Two mirrors are inclined at an angle as shown in the figure. light ray is parallel to one of the mirrors. The ray will s...The focal length of a concave mirror is 50 cm. where an object be placed so that its image is two times magnified, real ...A convex lens of Focal length of 40cm is in contact with a concave lens of focal length 25cm. The power of the combinati...