JEEAdvanced
For a certain metal, monochromatic light of wavelength 200 nm…
Question
For a certain metal, monochromatic light of wavelength 200 nm produces a stopping potential of 4.2 V, and light of wavelength 400 nm produces a stopping potential of 1.1 V. Treat hc as an unknown constant to be determined from the data along with the work function. Find the threshold wavelength (longest wavelength that ejects photoelectrons) in nm.
✓ Verified answer: 620checked by our engine — not a guess
Step-by-step solution
Einstein's equation: eV_stop = hc/lambda - phi. Write two equations:
hc/200 - phi = 4.2 ... (1)
hc/400 - phi = 1.1 ... (2)
Subtract (2) from (1): hc(1/200 - 1/400) = 3.1, i.e.
hc*(1/400) = 3.1, so hc = 1240 eV*nm.
From (2): phi = 1240/400 - 1.1 = 3.1 - 1.1 = 2.0 eV.
Threshold wavelength lambda_0 = hc/phi = 1240/2.0 = 620 nm.
Final answer620
Stuck on a problem like this?
Paste any JEE or NEET question — verified working, a confidence %, and an honest “not sure” instead of a bluff.
Solve my doubt →More Physics Modern Em solutions
Twelve identical resistors, each of resistance 12 ohm, are soldered…JEE · PhysicsAn infinite resistor ladder is built from identical repeating…JEE · PhysicsA resistor bridge has four nodes A, B, C, D. The resistors are: A-C =…JEE · PhysicsA bridge of capacitors has four nodes A, B, C, D with capacitances:…JEE · PhysicsTwo batteries are connected in parallel across an external resistor.…JEE · PhysicsCapacitor X (2 uF) is charged to 120 V and capacitor Y (3 uF) is…JEE · PhysicsA parallel-plate capacitor of capacitance 2 uF is connected to a 100…JEE · PhysicsA parallel-plate capacitor has plate separation d. A dielectric slab…JEE · Physics