Geometrical OpticsHard
Question
A convex lens forms an image of an object on a screen . The height of the image is 9 cm. The lens is now displaced until an image is again obtained on the screen. Then high of this image is 4 cm. The distance between the object and the screen is 90cm.
Options
A.The distance between the two positions of the lens is 30 cm
B.The distance of the object from the its first position is 36 cm
C.The height of the object is 6 cm
D.The focal length of the lens 21.6 cm
Solution
Height of object
=
Height of object = 6 cm
m1 =
u2 ≡ v1 =
v1 ∴ X = 
u1 - u1 = 
= X
D = 90 = u2 + u1 =
u1 + u1
u1 = 36 ⇒ X =
= 18
Distance between two position of lens = X = 18
Focal length f =
= 21.6 cm
=
Height of object = 6 cm
m1 =
u2 ≡ v1 =
v1 ∴ X = u1 - u1 = = XD = 90 = u2 + u1 =
u1 + u1u1 = 36 ⇒ X =
= 18Distance between two position of lens = X = 18
Focal length f =
= 21.6 cmCreate a free account to view solution
View Solution FreeMore Geometrical Optics Questions
Refractive index of violet,yellow and Red colour of light for a material of lens are 1.66, 1.64 & 1.62 respectively. If ...A transparent solid cylindrical rod has a refractive index of . It is surrounded by air. A light ray is incident at the ...A concave mirror of focal length f (in air) is immersed in water (μ = 4/3). The focal length of the mirror in water...A single slit Fraunhofer diffraction pattern is formed with white light. For what wavelength of light the third secondar...The Cauchy′s dispersion formula is...