Class 12 Physics Important Chapter 9 Ray Optics and Optical Instruments

Class 12 Physics Important Chapter 9 Ray Optics and Optical Instruments Solutions English Medium As Per The New Syllabus to each chapter is provided in the list so that you can easily browse through different chapters ASSEB Class 12 Physics Additional Solutions in English and select need one. NCERT Class 12 Physics Additional Solutions Download PDF. HS 2nd Year Physics Important Solutions.

Class 12 Physics Important Chapter 9 Ray Optics and Optical Instruments

Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. CBSE Class 12 Physics Additional Question Answer are part of All Subject Solutions. Here we have given HS 2nd Physics Important Solutions English Medium for All Chapters, You can practice these here.

Ray Optics and Optical Instruments

Chapter: 9

IMPORTANT QUESTION AND ANSWER

Answer The Following Questions:

1. State the conditions for the phenomenon of total internal reflection to occur.

Ans. (i) Light must travel from denser to rarer medium.

(ii) The angle of incidence in the denser medium must be greater than the critical angle for the two media.

2. What happens to the focal length of a convex lens, when it is immersed in water?

Ans. Focal length f of a convex lens is related to its refractive index as:

F ∝ 1/𝝁-1 

As ^ω𝜇_g ＜^a𝜇_g, so focal length of the convex lens will increase when it is immersed in water.

3. Two thin lenses of power + 5 D and -3D are in contact. What is focal length of the combination?

Ans. The equivalent power of the combination P = P₁ + P₂ = 5D – 3D = 2D 

∴ Focal length of the combination, 1/P 1/2 m = 50 cm.

4. What step can be taken to achieve high resolving power of a telescope?

Ans: To achieve high resolving power in a telescope, the aperture (diameter) of the objective lens or mirror should be increased. A larger aperture allows the telescope to collect more light, improving its ability to distinguish between two closely spaced objects.

5. State Snell’s law of refraction of light.

Ans: Snell’s law of refraction states that the ratio of the sine of the angle of incidence (iii) to the sine of the angle of refraction (r) is constant for any two given media:

Where:

v₁ and v₂​ are the speeds of light in the first and second mediums, respectively,
μ is the refractive index of the second medium relative to the first.

6. What is the range of wavelength of electromagnetic radiation that nature has endowed our retina to detect?

Ans: The range of wavelengths of electromagnetic radiation that the human retina can detect is approximately from 400 nm (violet) to 700 nm (red).

7. Why is a photodiode preferably used in the reverse bias condition for measuring light intensity?

Ans: A photodiode is used in reverse bias condition because, in reverse bias, it allows the generation of photocurrent when light falls on it. The reverse bias ensures that the photodiode operates in its most sensitive state, enabling accurate measurement of light intensity.

8. Mention the condition where Snell’s law of refraction cannot be satisfied.

Ans: Snell’s law of refraction cannot be satisfied when the angle of incidence exceeds the critical angle in a situation where light moves from a denser medium to a rarer medium. This leads to total internal reflection, where no refraction occurs, and all the light is reflected back into the denser medium.

9. State one difference between interference and diffraction.

Ans: Interference is the phenomenon that occurs when two or more waves combine to form a resultant wave, leading to constructive or destructive interference, while diffraction is the bending of waves around obstacles or the spreading of waves through openings.

10. Establish the following relation for total deviation δ\deltaδ of a ray of light refracted through a triangular glass prism.

Ans: The total deviation (δ\deltaδ) of a ray of light passing through a triangular prism is the angle by which the light is deviated from its original path after passing through the prism. 

The relation for total deviation is given as: 

δ = i + e − A

Where:

i is the angle of incidence (the angle between the incident ray and the normal to the surface of the prism),

e is the angle of emergence (the angle between the emergent ray and the normal to the surface of the prism),

A is the angle of the prism (the angle between the two faces of the prism).
The deviation depends on the angle of the prism and the refractive index of the material.

11. State two important differences between interference and diffraction.

Ans:Interference:

(i) Involves the interaction of two or more coherent waves.

(ii) Results in a pattern of constructive and destructive interference (bright and dark fringes).

Diffraction:

(i) Involves the bending of waves around obstacles or through openings.

(ii) Results in a spread of light or wavefront, forming diffraction fringes on a screen.