## Physics - Refraction From Lens

Q1: In refraction of light, what does Snell's Law state?

Answer: The ratio of sine of angle of incidence to the sine of angle of refraction remains constant subject to certain conditions. This is called refraction.

Q2: Which of the following property of light wave changes when it travels from one medium to another (having different optical densities)?

a. Wavelength
b. Speed of Light
c. Frequency

Answer: The frequency of a wave does not change as the wave passes from one medium to another. Both the speed and the wavelength do change, but the frequency remains the same.

Q3: Which of the following correctly represents the Snell's Law equation:
a. n₁sinθ₁ = n₂sinθ₂
b. n₁sinθ₂ = n₂sinθ₁
c. n₁tanθ₂ = n₂tanθ₁

Answer:  Option 'a' is correct i.e.  n₁sinθ₁ = n₂sinθ₂

Q4: What is the relation between aperture and radius of curvature of a typical thin lens?

Answer:  Aperture is much less than its radius of curvature for a thin lens.

Q5: When a ray of light passes through the optical centre (O) of a convex or concave lens, how will it emerge?

Answer: The emergent ray will have no deviation.

Q6: Fill in the blank.
The _______ length is the image distance that corresponds to an infinite object distance.

Answer: Focal length (Use lens formula, put v = ∞)

Q7:  When the object is between the focal point and a converging lens, where and what type of image will be formed?

Answer: When the object is between the focal point and a converging lens, the image is virtual, erect, larger than the object, and on the front side of the lens.

Q8: If the lens is used to form an image of the Sun on a screen, how far from the lens should the screen be located?

Q9: Take a concave lens and place it on the lens stand. Keep a burning candle on one side of the lens, observe its image by looking from the other side of the lens. Can you obtain the image on a screen? Why or Why not?

Answer:  It cannot be obtained on a screen. A concave lens always forms virtual, erect and diminished image irrespective of the object.

Q10: What is the power of a convex lens?

Q11: If a concave lens has power -2D, what is its focal length?

Q12: Magnification (m) for a concave lens is + 0.33. What type of image so formed?

Answer: The positive sign shows that the image is erect and virtual. The image is one-third of the size of the object.

Q13: What is the SI unit of power of a lens?