When a light of a given wavelength falls on a metallic surface the stopping potential for photoelectrons is 3.2 V. If a second light having wavelength twice of first light is used, the stopping potential drops to 0.7 V. The wavelength of first light is ____ m. (h=6.63×10−34 J.s,e=1.6×10−19C,c=3×108 m/s)
Held on 24 Jan 2026 · Verified 6 Jul 2026.
2.5×10−7
2.2×10−8
3.1×10−7
2.9×10−8
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