Math Problem Statement

A light ray in air was directed at the flat side of a semicircular glass block at an angle of incidence of 50degrees. The angle of refraction at the point of incidence was 30degrees. Calculate the refractive index of glass. Calculate the angle of refraction if the angle of incidence was changed to 60degrees

Solution

Part 1: Refractive Index of Glass

We can use Snell's Law to solve for the refractive index of the glass. Snell's Law states:

n1sinθ1=n2sinθ2n_1 \sin \theta_1 = n_2 \sin \theta_2

Where:

  • n1n_1 is the refractive index of air (which is approximately 1),
  • θ1\theta_1 is the angle of incidence in air,
  • n2n_2 is the refractive index of glass (the value we want to find),
  • θ2\theta_2 is the angle of refraction in glass.

Given data:

  • n1=1n_1 = 1 (since it's air),
  • θ1=50\theta_1 = 50^\circ (angle of incidence in air),
  • θ2=30\theta_2 = 30^\circ (angle of refraction in glass).

Applying Snell's Law:

1×sin(50)=n2×sin(30)1 \times \sin(50^\circ) = n_2 \times \sin(30^\circ)

Now, solve for n2n_2:

n2=sin(50)sin(30)n_2 = \frac{\sin(50^\circ)}{\sin(30^\circ)}

We know that sin(50)0.7660\sin(50^\circ) \approx 0.7660 and sin(30)=0.5\sin(30^\circ) = 0.5.

n2=0.76600.5=1.532n_2 = \frac{0.7660}{0.5} = 1.532

So, the refractive index of the glass is approximately 1.532.

Part 2: Angle of Refraction for a 60° Angle of Incidence

Now, we need to find the angle of refraction when the angle of incidence is changed to 60°.

We use Snell's Law again:

n1sinθ1=n2sinθ2n_1 \sin \theta_1 = n_2 \sin \theta_2

Substitute the known values:

  • n1=1n_1 = 1 (refractive index of air),
  • n2=1.532n_2 = 1.532 (refractive index of glass),
  • θ1=60\theta_1 = 60^\circ (new angle of incidence),
  • θ2\theta_2 is the angle of refraction in glass, which we need to find.

Using Snell's Law:

sin(60)=1.532×sin(θ2)\sin(60^\circ) = 1.532 \times \sin(\theta_2)

sin(60)0.8660\sin(60^\circ) \approx 0.8660

Now solve for sin(θ2)\sin(\theta_2):

sin(θ2)=sin(60)1.532=0.86601.5320.565\sin(\theta_2) = \frac{\sin(60^\circ)}{1.532} = \frac{0.8660}{1.532} \approx 0.565

Now find θ2\theta_2 by taking the inverse sine:

θ2=sin1(0.565)34.6\theta_2 = \sin^{-1}(0.565) \approx 34.6^\circ

Thus, the angle of refraction is approximately 34.6°.

Final Answer:

  • The refractive index of the glass is 1.532.
  • The angle of refraction when the angle of incidence is 60° is approximately 34.6°.

Would you like more details or clarifications on any part? Here are 5 related questions for further exploration:

  1. How would the refractive index change if the angle of incidence were larger than the critical angle?
  2. How does the refractive index affect the speed of light through a medium?
  3. What is the effect of a larger refractive index on the bending of light?
  4. How would the angle of refraction change if the material was denser than glass?
  5. How can we calculate the critical angle for total internal reflection?

Tip: When dealing with Snell's law, always ensure the angles are in the correct units (degrees or radians), and remember that the refractive index of air is nearly always taken as 1 unless otherwise stated.

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Math Problem Analysis

Mathematical Concepts

Optics
Refraction
Snell's Law

Formulas

n1 * sin(θ1) = n2 * sin(θ2)
sin(θ2) = sin(θ1) / n2

Theorems

Snell's Law

Suitable Grade Level

Grades 10-12