Question

Q.23. A man focused the image of a candle flame on a white screen by placing the flame at various distances from a convex lens. He noted his observation in a tabular form. On the basis of this table answer the questions given below- Observation no. Distance of the flame from the lens(cm) Distance of the screen from the lens (cm) 1 SS 20 1 S 18 20 30 30 15 lv 15 V 40 (0) What is the focal length of the convex lens? Which set of observation is incorrect and why?​

Answer 1

Explanation:

su=30 cm, v = 30 cm This is possible if the object is placed at 2f So, 2f =30 cm, f=15 cm (b) u=15 cm, v=70 cm is incorrect. This is because if the object is at focus then the image is formed at infinity. (c)In (lii) case, because the object is at the center of curvature.Read more on Sarthaks.com - https://www.sarthaks.com/165406/student-focused-image-candle-flame-white-screen-placing-flame-various-distances-convex

Answer 2

Answer:

A student focused the image of a candle flame on a white screen by placing the flame at various distances from a convex lens.

...

S. No. Distance of flame from the lens (cm) Distance of the screen from the lens (cm)

(ii) 40 24

(iii) 30 30

(iv) 24 40

(v) 15