Question

The air film in a Newton's ring apparatus is replaced by an oil film. The radii of the rings

• A. remains the same
• B. increases
• C. decreases
• D. none of the above

Answer 1

The correct option is C decreases

Radius of nth order Newton's ring is proportional to $\sqrt{\lambda }$ which decreases in oil since $\lambda =\frac{{\lambda }_{vacuum}}{\mu }$. Thus the radius of newton's ring decreases in oil film.