A student focused the image of a candle flame on a white screen by placing the flame at various distance from a convex lens. He noted his observation as mentioned in the following table.

Analyze the above table and answer the following questions.
If teacher asked the student to place the flame of candle at distance 20 cm from convex lens then, at what distance will the image be observed by the student?

Explanation

Given Object distance `(u)=-20 cm,`
focal length (f)=15 cm
To find Image distance (v)
Formula: `(1)/(f)=(1)/(v)-(1)/(u)`
Calculation: From Formula, `(1)/(v)=(1)/(f)+(1)/(u)=(1)/(15)+(1)/(-20)` brgt `=(1)/(60)`
`therefore" "v=60 cm`
Image will be observed at a distance of 60 cm.