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The difference between threshold wavelengths for two metal surfaces A and B having work function φ_A=9 eV and φ_B=4.5 eV in nm is (Given, hc=1242 eV nm)

Asked in JEE Main 13th April 1st Shift 2023 · Threshold frequency and wavelength

• (1) 540
• (2) 264
• (3) 276
• (4) 138

Step-by-step solution

Why the other options are wrong

• (1) comes from cannot be produced from the two work functions; check hc/φ for each metal first
• (2) comes from cannot be produced either; the two threshold wavelengths are 138 nm and 276 nm
• (3) comes from dividing hc by the difference of the work functions instead of differencing the two threshold wavelengths

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