Question 18 of 29intermediate🔧 ApplyMCQ1 mark

Which of the following lenses would you prefer to use while reading small letters found in a dictionary?

Exercise: EXERCISES | Q: 6 | (Page Page 26)
For More Understanding

Explanation

Option C is correct because for reading small letters, we need a magnifying glass which requires a convex lens with short focal length. The context states that power of a lens is inversely related to focal length (P = 1/f). A convex lens of focal length 5 cm has a power of P = 1/0.05 = +20 D, which is much higher than a convex lens of 50 cm (power = +2 D). Higher power means greater magnification. Concave lenses have negative power and cannot be used as magnifying glasses as they always produce diminished images.

Solution Steps

  1. Step 1: For reading small letters, we need a magnifying glass which requires a convex lens.

  2. Step 2: Power of lens P = 1/f (where f is in metres).

  3. Step 3: For convex lens of 5 cm: P = 1/0.05 = +20 D.

  4. Step 4: For convex lens of 50 cm: P = 1/0.5 = +2 D.

  5. Step 5: Higher power (+20 D) provides greater magnification, so convex lens of 5 cm is preferred.

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