CBSE 12th Board Exams to Be Held in a Week: Check CBSE 12th Physics Chapter 9 Important Questions

CBSE 12th Physics Chapter 9 Important Questions: The Central Board of Secondary Education (CBSE) will conduct the class 12 Board exams from Feb 15 till Apr 5, 2023. Therefore, interested students who plan to appear for the exam must go through the CBSE 12th Physics Chapter 9 Important Questions for preparation.

The Physics exam is scheduled to be conducted on Mar 6, 2023. Further, students completing their CBSE 12th Physics chapter 9 important questions must thoroughly study the ninth chapter, CBSE 12th physics ray optics, and optical instruments. Furthermore, the ninth chapter includes high-weightage questions from this section, so applicants must consider it for the CBSE 12th physics revision.

Also Read: CBSE 12th Physics Chapter 7 Important Questions

CBSE 12th Physics Chapter 9 Important Questions

Candidates must refer to the following to prepare for CBSE 12th Physics Chapter 9 Important Questions.

• Question 1. What must be the refractive index of the liquid if the Aglasslensof refractive index 1.5 is placed in a trough of liquid to mark the lens disappear? (Delhi 2008)
  Answer: In order to make the lens disappear the refractive index of liquid must be equal to 1.5 i.e. equal to that of glass lens.
• Question 2: What would be the focal length of the lens if a converging lens of refractive index 1.5 is kept in a liquid medium having same refractive index? (Delhi 2008)
  Answer: The lens in the liquid will act like a plane sheet of glass 
  

∴ Its focal length will be infinite (∞)

• Question 3: If the incident red light is replaced by violet light, how does the power of a convex lens vary? (Delhi 2008)
  Answer: According to Lens Maker’s formula
  
  ∴ power of the lens will be increased.
• Question 4: If the incident violet light is replaced with red light, how does the angle of minimum deviation of a glass prism vary (All India 2008)
  Answer: We know that λ red > λ violet, therefore µ red < µ violet and hence δ red < δ violet. When incident violet light is replaced with red light, the angle of minimum deviation of a glass decreases.
• Question 5: If immersed in a liquid of refractive index 1.3, how does the angle of minimum deviation of a glass prism of refractive index 1.5 change? (All India 2008)
  Answer:
  
  Hence angle of deviation is decreased.
• Question 6: What is the focal length of the Two thin lenses of power in combination of + 4D and – 2D are in contact? (All India 2009)
  Answer:
  
• Question 7: What is the value of the refractive index of the lens of a glass lens of refractive index 1.45 disappears when immersed in a liquid? (Delhi 2010)
  Answer: The value of refractive index of the liquid should be 1.45 so that the glass lens of refractive index 1.45 disappears when immersed in a liquid.
• Question 8: Mention the phenomenon of total internal reflection. (Delhi 2010)
  Answer: Two essential conditions for total internal reflection are :

1. Light should travel from an optically denser medium to an optically rarer medium.
2. The angle of incidence in the denser medium must be greater than the critical angle for the two media.

• Question 9: If two lenses of equal focal lengths are kept coaxially in contact with a diverging lens, what is the combination's focal length? (Delhi 2010)
  Answer: Focal length of the combination is Infinity.
• Question 10: If a medium's critical angle is 30°, what will be the speed of its light? (Delhi 2010)
  Answer:
  
  ∴ Speed of light, v = 1.5 × 10⁸ ms^-1