Practice question

Given: Calculate the number of photons emitted per second by a 25 W bulb emitting monochromatic light of wavelength 570 nm. ( h = 6.626 × 10⁻³⁴J s, c = 3.0 × __10POW₈__m s^{-1 ) These values define the system as per NCERT data. Formula: Energy per photon = hc/lambda = frac6.626 × 10⁻³⁴ × 3.0 × __10POW₈₅₇₀__ × 10⁻⁹= 3.487 × 10⁻¹⁹J. This is standard NCERT relation. Substitution & Calculation: Number of photons = frac253.487 × 10⁻¹⁹= 7.17 × __10POW₁₉__s^{-1 . Result: The computed value matches expected outcome and confirms correct choice as per NCERT.