JEE Main Optics – Topic Test

Topics in this test

Difficulty: 15 medium · 15 hard

Optics MCQ questions with answers

The first 3 of 30 questions. Unlock the series for the rest, each with a solution.

1. Q1. In a Young's double-slit experiment the slit separation is 0.25 mm, the screen is 1.5 m away, and light of wavelength 500 nm is used. The fringe width is:

   यंग के द्विझिरी प्रयोग में झिरियों के बीच की दूरी 0.25 mm है, पर्दा 1.5 m दूर है, और 500 nm तरंगदैर्घ्य का प्रकाश उपयोग किया गया है। फ्रिंज चौड़ाई है:

   • A. 3 mm
   • B. 0.3 mm
   • C. 6 mm
   • D. 1.5 mm
   Solution

   β = λD/d = (500×10⁻⁹ × 1.5)/(0.25×10⁻³) = 3×10⁻³ m = 3 mm.

   β = λD/d = (500×10⁻⁹ × 1.5)/(0.25×10⁻³) = 3×10⁻³ m = 3 mm।

2. Q2. A concave mirror of focal length 15 cm forms a real image that is twice the size of the object. The distance of the object from the mirror is:

   15 cm फोकस दूरी वाला एक अवतल दर्पण एक वास्तविक प्रतिबिंब बनाता है जो वस्तु के आकार का दोगुना है। दर्पण से वस्तु की दूरी है:

   • A. 30 cm
   • B. 22.5 cm
   • C. 7.5 cm
   • D. 45 cm
   Solution

   For a real inverted image, magnitude of magnification 2 gives v = 2u; using 1/v + 1/u = 1/f with f = -15 cm yields u = -22.5 cm, so the object is 22.5 cm from the mirror.

   एक वास्तविक उल्टे प्रतिबिंब के लिए, आवर्धन का परिमाण 2 होने से v = 2u प्राप्त होता है; f = -15 cm के साथ 1/v + 1/u = 1/f का उपयोग करने पर u = -22.5 cm मिलता है, अतः वस्तु दर्पण से 22.5 cm दूर है।

3. Q3. A convex lens of focal length 15 cm is to form a real image of a real object on a screen. The minimum possible distance between the object and the screen is:

   15 cm फोकस दूरी के एक उत्तल लेंस द्वारा किसी वास्तविक वस्तु का वास्तविक प्रतिबिम्ब पर्दे पर बनाना है। वस्तु तथा पर्दे के बीच न्यूनतम सम्भव दूरी है:

   • A. 60 cm
   • B. 30 cm
   • C. 75 cm
   • D. 45 cm
   Solution

   For a convex lens, a real image of a real object can be formed only if the object–screen separation is at least 4f. With f = 15 cm, the minimum separation is 4 × 15 = 60 cm, which occurs when the object and image are each 2f from the lens.

   उत्तल लेंस द्वारा वास्तविक वस्तु का वास्तविक प्रतिबिम्ब तभी बन सकता है जब वस्तु–पर्दा दूरी कम से कम 4f हो। f = 15 cm होने पर न्यूनतम दूरी 4 × 15 = 60 cm है, जो तब प्राप्त होती है जब वस्तु तथा प्रतिबिम्ब दोनों लेंस से 2f दूरी पर हों।

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