Which one of the following metals is used in the filaments of photo-el

Which one of the following metals is used in the filaments of photo-electric cells that convert light energy into electric energy ?

Tungsten

Copper

Rubidium

Aluminium

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This question was previously asked in

UPSC NDA-1 – 2018

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Photo-electric cells, which convert light energy into electrical energy via the photoelectric effect, utilize materials with low work functions. Alkali metals are known for their low work functions, meaning they easily emit electrons when illuminated by light of sufficient frequency. Among the given options, Rubidium is an alkali metal and is used in photoemissive surfaces in some types of photocells or photomultiplier tubes. Caesium is also very commonly used, often alloyed with other elements.

Alkali metals have low work functions, making them suitable for use as photoemissive materials in devices that rely on the photoelectric effect.

Tungsten is a refractory metal with a high melting point and is used as a filament in incandescent bulbs, but it has a high work function. Copper and Aluminium are conductors but are not typically used as primary photoemissive surfaces for converting light to electricity in this manner. Photocathodes in modern photomultiplier tubes often use complex alloys or semiconductor materials for optimized sensitivity to different wavelengths of light.

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