A tuning fork of frequency 256 Hz is struck and held near a closed organ pipe. Resonance occurs when pipe length is approx (v=340 m/s) MCQ with Answer and Explanation

Explanation:
Spectrometer measures wavelengths of light using diffraction gratings or prisms to disperse light and angular measurements. Interferometer (D) can also measure wavelength but spectrometer is the standard instrument for spectral analysis. Microscope and telescope magnify images, not measure wavelength. Memory tip: 'Spectrometer = wavelength measurement via dispersion; used in spectroscopy'. This instrument-application question tests practical physics knowledge, frequently examined in competitive exams. Always associate instruments with their primary function; competitive exams often test context-specific uses.

Explanation:
Range R = u²sin(2θ)/g = (20)²×sin(60°)/10 = 400×(√3/2)/10 = 20√3 m. Formula applies for level ground projection. Memory tip: sin(2θ) for θ=30° is sin60°=√3/2. Standard projectile calculation frequently appearing in competitive exams with trigonometric values.

Explanation:
Dispersion happens because refractive index varies with wavelength. Prism, rainbow. Scattering is Tyndall effect (blue sky). Polarisation restricts vibrations.