JEE Advanced Model Paper 16 with solutions for online practice

When a certain metallic surface is illuminated with monochromatic light ofwavelength λ , the stopping potential for photoelectric current is 3 V0 and when thesame surface is illuminated with light of wavelength 2 λ , the stopping potential is V0 . The threshold wavelength of this surface for photoelectric effect is K λ . Calculate thevalue of K.