In a transistor, the collector current is 1 mA and base current 10 μA. Emitter current is MCQ with Answer and Explanation

Explanation:
ρ = R A / L, unit Ω m.

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:
Convex mirrors bulge outwards, which inherently provides a much wider field of view compared to plane mirrors. Regardless of the object's position, a convex mirror reliably produces virtual, erect, and diminished (smaller) images. This allows a driver to see a large area of the road behind them in a small mirror, making R the exact explanation for A.