Which one of the following lenses would you prefer to use while reading very small letters printed on a label ?
Convex lens of large focal length
Concave lens of large focal length
Convex lens of small focal length
Concave lens of small focal length
Answer is Right!
Answer is Wrong!
This question was previously asked in
UPSC CAPF – 2009
To read small letters, a magnifying glass is used. A magnifying glass is a convex lens. A convex lens forms a magnified, virtual, and erect image when the object is placed within its focal length. The magnification power of a simple magnifying glass is given by M = 1 + (D/f), where D is the least distance of distinct vision (approx. 25 cm) and f is the focal length of the lens. To achieve higher magnification, the focal length (f) must be smaller.