Q192 / 200 · MHT CET - Medical 2026 (21 April Shift 2) · Physics
In a single slit diffraction pattern, identify the incorrect statement from the following
- AThe fringes have unequal width.
- BThe fringes have unequal intensity.
- CThe fringes have unequal width and unequal intensity.
- Correct answerDThe fringes have equal width and equal intensity.
Solution
In a single slit diffraction pattern, the central maximum has an angular width of $\dfrac{2\lambda}{a}$, whereas the secondary maxima have an angular width of $\dfrac{\lambda}{a}$. Thus, the fringes have unequal widths.
The intensity of the central maximum is maximum, and the intensity of the successive secondary maxima decreases rapidly (approximately $\dfrac{I_0}{22}$, $\dfrac{I_0}{61}$, etc.). Thus, the fringes have unequal intensities.
Therefore, the statement that the fringes have equal width and equal intensity is incorrect.
Answer: The fringes have equal width and equal intensity.
The intensity of the central maximum is maximum, and the intensity of the successive secondary maxima decreases rapidly (approximately $\dfrac{I_0}{22}$, $\dfrac{I_0}{61}$, etc.). Thus, the fringes have unequal intensities.
Therefore, the statement that the fringes have equal width and equal intensity is incorrect.
Answer: The fringes have equal width and equal intensity.
Hence, the correct answer is option: 'D'.