A beam of light in glass (n=1.5) strikes the glass-air interface at an angle of
Practice Questions
Q1
A beam of light in glass (n=1.5) strikes the glass-air interface at an angle of 60°. Will total internal reflection occur?
Yes
No
Only if the angle is increased
Only if the angle is decreased
Questions & Step-by-Step Solutions
A beam of light in glass (n=1.5) strikes the glass-air interface at an angle of 60°. Will total internal reflection occur?
Correct Answer: No, total internal reflection will not occur.
Step 1: Identify the refractive index of glass, which is given as n = 1.5.
Step 2: Use the formula for the critical angle, which is sin(θc) = 1/n.
Step 3: Substitute the value of n into the formula: sin(θc) = 1/1.5.
Step 4: Calculate 1/1.5, which equals approximately 0.6667.
Step 5: Find the critical angle θc by taking the inverse sine (arcsin) of 0.6667.
Step 6: Calculate θc, which is approximately 41.8°.
Step 7: Compare the angle of incidence (60°) with the critical angle (41.8°).
Step 8: Since 60° is greater than 41.8°, conclude that total internal reflection will not occur.
Total Internal Reflection – Total internal reflection occurs when light attempts to move from a denser medium to a less dense medium at an angle greater than the critical angle.
Critical Angle Calculation – The critical angle is calculated using the formula sin(θc) = 1/n, where n is the refractive index of the denser medium.
Refraction and Angles – Understanding the relationship between the angle of incidence and the angle of refraction at the interface of two media.
