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NEET-XII-Physics
09: Ray Optics And Optical Instruments
- #8A beam of light converges at a point P. Now a lens is placed in the path of the convergent beam 12 cm from P. At what point does the beam converge if the lens is (a) a convex lens of focal length 20 cm, and (b) a concave lens of focal length 16 cm?Ans : In the given situation, the object is virtual and the image formed is real.
Object distance, u = +12 cm
(a) Focal length of the convex lens, f = 20 cm
Image distance = v
According to the lens formula, we have the relation:
Hence, the image is formed 7.5 cm away from the lens, toward its right.
(b) Focal length of the concave lens, f = -16 cm
Image distance = v
According to the lens formula, we have the relation:
Hence, the image is formed 48 cm away from the lens, toward its right.
- #8-aa convex lens of focal length 20 cm, andAns : Focal length of the convex lens, f = 20 cm
Image distance = v
According to the lens formula, we have the relation:
Hence, the image is formed 7.5 cm away from the lens, toward its right.
- #8-ba concave lens of focal length 16 cm?Ans : Focal length of the concave lens, f = -16 cm
Image distance = v
According to the lens formula, we have the relation:
Hence, the image is formed 48 cm away from the lens, toward its right.