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Which of the following statements are true? (i) The principal focus of a converging lens is real. (ii) The principal focus of a diverging lens is virtual. (iii) The principal focus of a lens is always along the principal axis.

Which of the following statements are true? (i) The principal focus of a converging lens is real. (ii) The principal focus of a diverging lens is virtual. (iii) The principal focus of a lens is always along the principal axis. Correct Answer (i), (ii) and (iii)

CONCEPT:

  • Concave lens: It is a diverging lens that diverges the parallel beam of light.
    • It can also gather light from all directions and project it as a parallel beam.
    • The focal length of the concave lens is negative.
    • It has a virtual focus from the diverging rays of light that seem to converge.
  • Convex lens: The lens whose refracting surface is upside is called a convex lens.
    • The convex lens is also called a converging lens.
    • The focal length of a convex lens is positive

​EXPLANATION:

  • When parallel rays of light pass through a convex lens the refracted rays converges to one point called the principal focus. Hence, the principal focus of a converging lens is real. Therefore statement 1 is correct.
  • When parallel rays of light pass through a concave lens the refracted rays diverge so that they appear to come from one point called the principal focus, hence, the principal focus of a diverging lens is virtual. Therefore statement 2 is correct.
  • The principal focus of a lens is always along the imaginary line called the principal axis. Therefore statement 3 is correct.

Related Questions

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