The part of human eye that controls amount of light entering is MCQ with Answer and Explanation

Explanation:
The acceleration due to gravity at a depth 'd' is given by g' = g(1 - d/R), where R is the radius of the Earth. If we go to the center of the Earth, the depth 'd' becomes exactly equal to R. Substituting d = R into the formula gives g' = g(1 - R/R) = g(1 - 1) = 0. So, gravity is zero at the core.

Explanation:
Proton mass ≈ 1.67 × 10⁻²⁷ kg, electron ≈ 9.11 × 10⁻³¹ kg, ratio ≈ 1836. Neutron slightly heavier. Atomic mass concentrated in nucleus.

Explanation:
Screw gauge typically has least count 0.001 cm (0.01 mm). Vernier calliper least count 0.01 cm. Metre scale 0.1 cm. So screw gauge most precise.