# JAC 12th Physics Important Questions 2023 Ch9 Ray Optics

## JAC 12th Physics Important Questions 2023 Ch9: झारखण्ड बोर्ड कक्षा 12th सभी विद्यार्थियों के लिए Physics Unit 6. Optics में Chapter 9 Ray Optics के पिछले वर्षो में जो भी प्रश्न पूछे गए हैं, उनकी चर्चा हम इसमें करेंगे तो इन Important Questions को पढ़ लीजिए.

रांची: झारखंड एकेडमिक काउंसिल ( JAC Board) कक्षा JAC 12th Physics Important Question के पिछले वर्षों के सभी महत्वपूर्ण प्रश्न (important Questions) आपको यहाँ पर बताए जा रहे है, जो बोर्ड परीक्षा 2023 के लिए बहुत महत्वपूर्ण है. अगर आप इन सभी प्रश्नों को याद कर लेते हो तो अवश्य ही आप JAC Board class 12th Physics exam 2023 में अच्छे अंक प्राप्त कर सकते हो.

यदि आप ऐसे ही सभी विषयों के Chapterwise Important Questions उत्तर चाहते हैं तो हमारे वेबसाइट jharkhandlab.com से जुड़े रहे.

विद्यार्थी इसका उत्तर स्वयं करें। ये सारे प्रश्न आपके परीक्षा (JAC 12th Physics Important Question For Board Exams)में बार – बार पूछे जा रहे है। इसमें आपको सभी chapter का अलग-अलग पिछले 16 से 17 वर्षों के महत्वपूर्ण प्रश्न मिलेंगे। यानि 2006-2022 इसमें आपको ये भी बताया जा रहा है कि कौन से प्रश्न किस तरह से एवं कितने marks के पूछे जा रहें है.

यदि वैसे छात्र छात्राएं जो प्रश्नों के उत्तर नहीं कर पाते हैं, वो कुछ दिन प्रतीक्षा करें. आप यहाँ से Questions-answers डाउनलोड कर सकते हैं.

### JAC 12th Physics Previous Years Important Questions :

Q1. Two lenses of powers –7D and –2.5D are placed in contact . Find the focal length of the combination. (2 marks) [JAC –2006]
Q2. A compound microscope consists of two convex lenses of focal length 2.5cm and 18cm. An object is placed at a distance of 3.0 cm from the objective and the final image is formed at least distance of distinct vision. Find the magnification produced and distance between lenses.(5 marks) [JAC –2006]
Q3. The refrective index of glass is 3/2 and that of water is 4/3 . If the speed of light in glass is 2.0× 108m/s , what is the speed of light in water. (2 marks)[JAC –2007]

Q4. A convex lens of focal length 25cm and made of glass(??=1.50) is immersed in water(?? =1.33) . Find the change in the focal length of the lens. (3 marks) [JAC –2007]
Q5. With the help of ray daigram , explain the formation of image in a compound microscope. Derive an expression for its magnifying power when the image is formed at the least distance of distinct vision. (5 marks) [JAC –2007, 2009, 2012, 2017]
Q6. The velocity of light in a liquid is 1.5× 108m/s and in air it is 3× 108m/s. If a ray of light passed from this liquid to air. Calculate the value of critical angle. (2 marks) [JAC –2008]

Q7. State the condition for total internal reflection. (2 marks)
Q8. The focal length of concave lens is made of glass (?? = 1.5) in air is 15cm. Find the focal length of the lens in water(?? = 4/3).(2 marks)
Q9. A thin prism of 2° angle gives a deviation of 1° . What is the value of refrective index of material of the prism? (2marks) [JAC 2010]

Q10. What is the effect of increasing the diaameter of the objective of a telescope on its magnifying power ? (2 marks) [JAC –2010]

Q11. Calculate the speed of light is glass refractive index 1.5. Given the speed of light in air is 3×108 m/s. (3 marks) [JAC –2010]

Q12. On what factors does the focal length of lens depend? (2 Marks)[JAC –2011]

Q13. The angle of minimum deviation for prism of angle 60° is 30°. Calculate the velocity of light in a material of the prism, if speed of light in vacuum is 3×108 m/s. (3 marks) [JAC –2011]

Q14. What is first and second focus of lens? Establish the following lens formula : (5 marks) 1/? = (? − 1) ( 1/?1 − 1/?2) [JAC –2011, 2013]

Q15. A convex lens of focal length 40cm is placed in contact with a concave lens of focal length 20cm. What is the equivalent focal length of combination. (3 Marks)[JAC –2012]

Q16. Write advantage of reflecting telescope over a refracting telescope telescope. (3 Marks ) [JAC –2012]

Q17. Derive the formula 1/? = 1/? + 1/? for a convex mirror. (5 Marks) [JAC –2012]

Q18. Find the relation between critical angle and refractive index.(2 marks)[JAC –2013]

Q19. A short sighted person uses lens for observing object at a distance of 200cm but he can see any object at a distance of 20cm without any use of lens. Find the focal length and nature of correcting lens required. Also find the power of correcting lens. (3 Marks) [JAC 2013]
Q20. When lens immersed in water its focal length – (1 marks)[JAC-2014]
a) increases
b) decreases
c) remain same
d) none of these
Q21. The magnification produced by an Astronomical telescope in normal adjustment is – (1 marks) [JAC-2014]
a) ?? ??
b) ?? ′??
c) ?? /??
d) ?? /??

Q22. Which of the following phenomena explains that light does not travel in straight line ? (1 marks)[JAC-2014]
a) Reflection
b) Refraction
c) Diffraction
d) Polarisation
Q23. What is equivalent lens ? The equivalent focal length of two thin lenses in contact is 20cm. If power of one lens is ( -3D), find the focal length of other lens. (1+2=3 Marks) [JAC –2014, 2022]
Q24. Find the condition that a combination of two thin prism, produces no deviation. Hence, in the depression produced by the combination. (2+1=3 Marks) [JAC –2014]

Q25. For refraction at any curved surface , establish the relation ,
?2/? − ?1/? = (?2−?1)/? , where terms have usual meanings. (5 Marks) [JAC –2014, 2016]
Q26. In white light spectrum produced by depression through a prism , the ray that is deviated least is – (1 marks)[JAC -2015]
a) yellow
b) blue
c) green
d) red
Q27. Diopter is a unit for–(1marks) [JAC -2015]
a) focus of a lens
b) focal length of a lens
c) power of lens
d) magnifying power

Q28. When a white ray of light passes through a prism it is dispersed Why? Why is red colour deviated least in a prism but voilet colour is deviated most? (3 Marks) [JAC –2015]
Q29. What is equivalent lens ? Find the equivalent focal length for a system of two thin lenses in contact. (5 Marks) [JAC–2015,2018, 2022]
Q30. Define critical angle . Mention the condition for internal reflection of light. (2 Marks)[JAC –2016]

Q31. The length of an astronomical telescope in normal adjustment is (1 marks) [JAC –2017]
a) ?? − ??
b) ?? × ??
c) ?? + ??
d)??/??
Q32. Focal length of a convex lens in air is 20 cm. Find its focal length when immersed in water. Given ?? =2/3 , ?? = 4/3 . (3 marks) [JAC –2017]

Q33. The far point of a myopic person is 70 cm in front of eye . Calculate the focal length and power of lens needed by him to see the distanct object clearly. (3 marks) [JAC –2018]
Q34. For refraction through a thin lens, derive the relation
1/? = (( ?2/?1)—1)( 1/?1 − 1/?2) , where the term have usual meanings. (5 marks)[JAC-2018, 2020]
Q35. In an astronomial telescope focal legth of two lenses are 0.3mm and 0.5mm. In normal adjustment the distance between is (1 marks)[JAC 2019]

a) 0.25m
b) 0.175m
c) 0.35m
d) 0.15m
Q36. A 4.5 cm needle is placed 12cm away from a convex mirror of focal length 15 cm. Give the location of the image and determine the magnification. (3 marks)[JAC-2019]
Q37.What is the angle of minimum deviation? For refraction of light through a prism, establish the relation ? = ??? ((?+??)/2)/??? ( ?/2 ) ; where term have usual meaning. (5 marks) [JAC – 2019]

Q38. If the refractive index of water and glass are 4/3 ??? 1/3 respectively. The refractive index of glass with respect of water is-(1 mark)[JAC-2020]
a)1/2
b) 9/8
c) 8/9
d) 2
Q39. If the focal length of objective lens of astronomical telescope is 20cm and the lemgth of its 25cm, the magnification of telescope for normal adjustment is- (1 mark)[JAC-2020]
a) 5
b) 4
c) 1.5
d) 1
Q40. An object is placed at a distance of 60 cm from a concave lens of focal length 15cm. Determine the magnification of lens. (3 marks)[JAC 2020]

Q41. Define linear magnification of lens. (2022)
Q42. Draw a compound microscope. Deduce an expression for its magnifying power when the image is formed at near point. (2022)

### JAC 12th Physics Important Questions Chapterwise List : 