Question

A converging lens with a focal length of 12 cm forms a real image of 8 mm tall, 17 cm to the right of the lens. (a) Determine the position and size of the object (b) Is the image upright or inverted? (c) Are the object and image on the same side or opposite sides of the object? (d) Draw a ray-diagram for this situation

Answer 1

Given,

focal length,f = 12cm

image distance, v =17 cm

image height, h' = 8mm = 0.8 cm

let us consider, object distance be u and object height be h

(a)

Using lens formula

u=40.8 cm (object position)

we know

Magnification,M = -v/u = h'/h

i.e. h=-(h'xu)/v = -(0.8x40.8)/17= -1.92cm

(b)Since M = -v/u= -40.8/12 = -3.4 is negative so Image is inverted.

(c)Since both u and v are positive so object and image on opposite sides of the object.

(d)

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