Youngs Double Slit Experiment YDSE - UNSOLVED PRACTICE SET
Chapter: Wave Optics | Topic: Youngs Double Slit Experiment YDSE
YOUNGS DOUBLE SLIT EXPERIMENT YDSE - UNSOLVED PRACTICE SET
Topic: Youngs Double Slit Experiment YDSE
Multiple Choice Questions
Q1. In Young's double slit experiment, the fringe width is given by:
- Ī² = Ī»D/d
- Ī² = Ī»d/D
- Ī² = D/(Ī»d)
- Ī² = d/(Ī»D)n D
Q2. The central fringe in YDSE is always:
- Dark
- Bright
- Alternating bright and dark
- Of zero width
Q3. If the separation between the two slits in YDSE is decreased, the fringe width:
- Decreases
- Increases
- Remains unchanged
- Becomes zero
Q4. In YDSE, the intensity at a bright fringe is:
- Equal to the intensity of a single slit
- Twice the intensity of a single slit
- Four times the intensity of a single slit
- Zero
Q5. When white light is used in YDSE:
- Only white and black fringes are obtained
- Coloured fringes are obtained with a white central fringe
- No fringes are obtained
- Only red fringes are obtained
Q6. The path difference for the nth bright fringe in YDSE is:
- nĪ»/2
- nĪ»
- (2n + 1)Ī»/2
- (2n ā 1)Ī»/2
Short Answer Questions
Q7. Describe Young's double slit experiment with a diagram. What does it demonstrate about the nature of light?
Q8. Why are bright and dark fringes formed in YDSE? Explain in terms of path difference.
Q9. What happens to the interference pattern in YDSE if:
(a) The screen is moved closer to the slits?
(b) One of the slits is covered?
Q10. Why is the central fringe in YDSE always bright when using monochromatic light?
Q11. In YDSE, the fringe width is found to be 0.5 mm. If the wavelength of light is 600 nm and the slit separation is 0.3 mm, calculate the distance of the screen from the slits.
Q12. Why does the intensity of bright fringes in YDSE vary gradually, reaching maximum at the centre of each bright fringe?
Long Answer Questions
Q13. Describe Young's double slit experiment. Derive the expression for the fringe width and explain the conditions for obtaining bright and dark fringes.
Q14. Derive the expression for the intensity distribution in Young's double slit experiment. Show that the intensity varies from maximum to minimum values and find the ratio of maximum to minimum intensity.
Q15. Explain what happens in Young's double slit experiment when:
(a) The source is moved closer to the slits
(b) One slit is made wider than the other
(c) White light is used instead of monochromatic light
Numerical & Application-Based Problems
Q16. In a Young's double slit experiment, the separation between the slits is 0.5 mm and the distance from the slits to the screen is 2 m. Light of wavelength 600 nm is used.
(a) Calculate the fringe width.
(b) Calculate the distance of the 5th bright fringe from the central fringe.
(c) Calculate the distance between the 3rd bright fringe and the 3rd dark fringe.
(d) If the entire apparatus is immersed in water (n = 4/3), calculate the new fringe width.
Q17. In YDSE, the distance between the slits is 0.2 mm and the distance to the screen is 1.5 m. The 4th bright fringe is observed at a distance of 1.8 cm from the central fringe.
(a) Calculate the wavelength of light used.
(b) Calculate the distance of the 6th dark fringe from the central fringe.
(c) If the wavelength is changed to 500 nm, keeping other parameters the same, calculate the new position of the 4th bright fringe.
Q18. In your school's physics lab, a student performs Young's double slit experiment using a laser pointer (Ī» = 650 nm) and a double slit with separation 0.4 mm. The screen is placed 2.5 m away.
(a) Calculate the fringe width observed on the screen.
(b) The student measures 10 fringe widths to be 4.06 cm. Calculate the experimental value of fringe width and compare it with the theoretical value. Calculate the percentage error.
(c) The student then places a thin transparent sheet of thickness 2 Ī¼m and refractive index 1.5 in front of one slit. Calculate the shift of the central fringe.
(d) A classmate suggests using sunlight instead of the laser. Predict what the interference pattern would look like and explain why the central fringe appears white.
(e) In the JEE (Main) examination, questions on YDSE often test conceptual understanding. A question states: 'If the intensity of one slit is reduced to half, what happens to the interference pattern?' Analyze this situation and describe the changes in the pattern.