EAMCET Engineering 2007 Solved Paper

In an experiment on photoelectric emission from a metallic surface, wavelength of incident light is 2×10−7m and stopping potential is 2.5V. The threshold frequency of the metal (in Hz ) approximately (charge of electron e=1.6×10−19C,‌‌ Planck's constant h=6.6×10−34J− s )