This question tests double-slit interference. The positions of bright fringes in double-slit interference are determined by the path difference condition: bright fringes occur where path difference equals integer multiples of the wavelength. This geometric condition depends only on slit separation, wavelength, and screen distance, not on the individual wave amplitudes. Partially covering one slit reduces its amplitude, which decreases the contrast between bright and dark fringes, but doesn't change their positions. Choice C incorrectly assumes that equal intensities are required for any interference to occur. The key insight is that fringe positions depend on geometry and wavelength, not on relative intensities.

This question tests understanding of double-slit interference. In double-slit interference, the spacing between adjacent bright fringes on the screen depends on three factors: wavelength (λ), slit separation (d), and distance to the screen (L). The fringe spacing is proportional to λL/d, meaning it increases when wavelength increases, when screen distance increases, or when slit separation decreases. Since the question asks for increased fringe spacing without calculation, increasing the distance to the screen (choice A) will spread the pattern out, making fringes farther apart. Choice B incorrectly suggests that intensity affects fringe spacing—intensity only changes the brightness of the pattern, not the geometric spacing. The key insight is that fringe spacing is a geometric property determined by the ratio of wavelength and slit separation, scaled by the screen distance.

This question tests understanding of double-slit interference. When light from two coherent slits travels different distances to reach a point on the screen, the path difference determines whether the waves arrive in phase or out of phase. A path difference of 1.5λ means one wave has traveled exactly one and a half wavelengths more than the other, creating a phase difference of 540° or equivalently 180° (since 360° = one full cycle). When waves arrive 180° out of phase, they interfere destructively, creating a dark fringe. Choice C incorrectly suggests that intensity affects fringe locations, but fringe positions depend only on path difference and wavelength, not intensity. To solve interference problems, remember that path differences of nλ (where n is an integer) produce bright fringes, while path differences of (n + 0.5)λ produce dark fringes.

This question tests double-slit interference. A laser produces highly coherent light, meaning the waves maintain a constant phase relationship, which is essential for stable interference patterns. A filament bulb without a filter emits incoherent white light with many wavelengths and random phase relationships. This lack of coherence causes the interference patterns from different wavelengths and phase relationships to overlap and average out, largely washing out the distinct bright and dark fringes. Choice C incorrectly assumes that slit independence maintains sharp fringes, missing that coherence between slits is crucial. Remember that stable interference patterns require coherent light sources.

This question tests understanding of double-slit interference. In double-slit experiments, the interference pattern depends on the path difference between waves from the two slits. A path difference of 5λ/2 equals 2.5λ, which can be written as 2λ + λ/2. Since 2λ represents two complete wavelength cycles (720° = 0° phase difference), the effective phase difference is just from the remaining λ/2, which equals 180°. Waves arriving 180° out of phase interfere destructively, creating a dark fringe at point V. Choice A incorrectly assumes that any path difference greater than λ produces a bright fringe, ignoring the cyclic nature of wave phase. Remember that path differences of (n + 0.5)λ always yield dark fringes, regardless of how large n is.

This question tests understanding of double-slit interference. In double-slit interference, bright fringes occur when waves from both slits arrive in phase (constructive interference), which happens when the path difference equals an integer multiple of the wavelength (0, λ, 2λ, etc.). Dark fringes occur when waves arrive out of phase (destructive interference), which happens when the path difference equals a half-integer multiple of the wavelength (λ/2, 3λ/2, etc.). The question states that the point currently has a path difference of λ/2, creating a dark fringe. To make this point bright, we need to change the path difference to an integer multiple of the wavelength. Choice A incorrectly suggests that changing intensity affects interference patterns—intensity only affects brightness, not the locations of bright and dark fringes. The key strategy is to remember that interference patterns depend on path difference relative to wavelength, not on the absolute intensity of light.

This question tests understanding of double-slit interference. Double-slit interference requires coherent light sources, meaning the waves from both slits must maintain a constant phase relationship over time. A laser provides coherent light because all photons are in phase, but an ordinary filament bulb emits incoherent light where the phase varies randomly and rapidly. Without coherence, the interference pattern changes too quickly to be observed, resulting in a uniform illumination instead of stable bright and dark fringes. Choice B incorrectly suggests that high intensity is needed for dark fringes—dark fringes form from destructive interference regardless of source intensity. The critical requirement for observable interference is temporal coherence, ensuring that the phase relationship between waves from the two slits remains constant.

This question tests understanding of double-slit interference. At the center of a double-slit pattern, where the path difference equals zero, waves from both slits travel exactly the same distance to reach point U. With zero path difference, the waves arrive perfectly in phase (0° phase difference) and interfere constructively, creating the central bright fringe. This is always the brightest point in the pattern because the waves add with maximum amplitude. Choice A incorrectly claims that equal paths cause cancellation, but waves only cancel when they arrive 180° out of phase. The fundamental principle is that zero path difference always produces maximum constructive interference, regardless of wavelength or slit separation.

This question tests double-slit interference requirements, specifically the need for coherent light. A laser produces coherent light (constant phase relationship), enabling stable interference patterns. A filament bulb emits incoherent light with rapidly changing phase relationships, preventing sustained constructive and destructive interference. Without coherence, the interference pattern disappears, leaving only the overlapping diffraction patterns from each slit. Choice A incorrectly assumes diffraction alone produces sharp fringes, but interference requires coherence. The strategy is to remember that stable interference patterns require coherent sources with fixed phase relationships.

This question tests understanding of double-slit interference. In double-slit interference, the spacing between adjacent bright fringes is given by Δy = λL/d, where λ is wavelength, L is screen distance, and d is slit separation. When slit separation d is reduced while keeping λ and L constant, the fringe spacing Δy increases inversely with d. This means adjacent bright fringes become farther apart on the screen as the slits move closer together. Choice B incorrectly predicts the opposite effect—this misconception often arises from thinking that closer slits should produce closer fringes. The transferable principle is that fringe spacing is inversely proportional to slit separation: smaller slit separation produces larger fringe spacing.