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10 Questions 10 Marks 10 Mins
CONCEPT:
- A convex lens is a spherical surface Lens that helps in converging all the light at a single point.
- An image formed is erect and virtual. Enlarged if the object is placed between lens and 2F and otherwise Diminished.
- The focal length of the Convex Lens is Positive.
- The relation between the distance of the image, object, and focal length is
\(\frac{1}{f}=\frac{1}{v}-\frac{1}{u}\),
where f is focal length, v is the distance of the image, and u is the distance of the object.
- The magnification is given as,
\(\Rightarrow m=\frac{-v}{u}=\frac{h_{I}}{h_{o}}\)
Where hI = height of the image and ho = height of the object
SOLUTION:
Given: f = 15 cm, v = -u
\(\frac{1}{15}=\frac{1}{-u}-\frac{1}{u} \Rightarrow \frac{1}{15}=\frac{-2}{u} \Rightarrow u=-30~cm\)
- Hence, the object should be placed at a distance of 30 cm from the lens.
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