$A$ person needs a lens of power $-0.5 \text{ D}$ for correcting his distant vision. For correcting his near vision,he needs a lens of power $+1.5 \text{ D}$. What is the focal length of the lens required for correcting his $(i)$ distant vision,$(ii)$ near vision?

• A
  $f_1 = -2 \text{ m}, f_2 = +0.67 \text{ m}$
• B
  $f_1 = -0.5 \text{ m}, f_2 = +1.5 \text{ m}$
• C
  $f_1 = +2 \text{ m}, f_2 = -0.67 \text{ m}$
• D
  $f_1 = -1 \text{ m}, f_2 = +0.5 \text{ m}$