Question

Figure shows a thin convex lens of focal length 20 cm with its optical centre at (50 cm, 0) and
principal axis along X-axis. If co-ordinates of a point object is (20 cm, 5 cm), then co-ordinates of its
image formed by the lens will be
(1) (150cm, -25 cm)
(2) (100cm, 25 cm)
(3) (110cm, -10cm)
(4) (60 cm, 20cm)

Solution with explanation.Please don't forget to add explanation or else I won't understand.
***please ignore the pen marks in the photo, I know its wrong what ever I drew there, just ignore those marks***

No irrelevant answers please....​

Answer 1

option (3) is correct choice.

explanation : focal length of convex lens , f = +20cm

position of optical centre is (50cm, 0)

position of object in co-ordinate system is (20cm,5cm)

so, object distance, u = -(50cm - 20cm) = -30cm

size of object, h_o = +5cm

now using formula, 1/v - 1/u = 1/f

⇒1/v - 1/-30 = 1/1/20

⇒1/v = 1/20 - 1/30 = 1/60

⇒v = +60cm

so, position of image = +60cm + 50cm = 110cm

now magnification , m = v/u = height of image/height of object

⇒60/-30cm = height of image/5cm

⇒height of image = -10cm [ negative sign shows image form below the x-axis]

so, co-ordinate of its image is (110cm,-10cm).

option (3) is correct choice.

also read similar questions :

Rohit focused the image of a candle flame on a white screen using a convex lens.He noted down the position of the...

https://brainly.in/question/1558065

Rohit focused the image of a candle flame on a white screen using a convex lens. He noted down the position of the candl...

https://brainly.in/question/2951657