Question

A ray of light is incident on a glass sphere from water as shown. If m_glass = $\frac { 3 } { 2 }$ and m_water= $\frac { 4 } { 3 }$ . The angle of incidence q so that the ray which enters the sphere does not come out of the sphere is –

• A. tan^–1$\left( \frac { 8 } { 9 } \right)$
• B. 90⁰
• C. tan^–1 (2)
• D. sin^–1$\left( \frac { 64 } { 81 } \right)$

Answer 1

Answer: (B)

90⁰

Answer 2

In DAOB

AO = OB

Ž Šr = Šc

m_w sin q = m_g sin c …. (1)

& sin c = $\frac { \mu _ { \mathrm { w } } } { \mu _ { \mathrm { g } } }$ …. (2)

\ sin q = $\frac { \mu _ { \mathrm { g } } } { \mu _ { \mathrm { w } } }$ × $\frac { \mu _ { \mathrm { w } } } { \mu _ { \mathrm { g } } }$

Ž q = 90⁰