The energy of a single photon is given by E = hc/λ, where h is Planck's constant, c is the speed of light, and λ is the wavelength. This relationship shows that shorter wavelengths correspond to more energetic photons. Calculating the energy per photon: E = (6.626 × 10^-34 × 3 × 10^8) / (300 × 10^-9) = (1.988 × 10^-25) / (3 × 10^-7) = 6.626 × 10^-19 J per photon. To deliver a total energy of 1 J, the number of photons required = 1 / (6.626 × 10^-19) = 1.509 × 10^18 ≈ 1.51 × 10^18 photons. Option 4.52 × 10^18 corresponds to using λ = 900 nm, incorrectly tripling the wavelength. Option 6.02 × 10^18 is close to Avogadro's number, representing a conceptual confusion with mole calculations. Option 3.02 × 10^18 arises from using λ = 600 nm instead of 300 nm. This problem tests the photon energy formula E = hc/λ, a standard topic connecting electromagnetic radiation to quantum theory in JEE. Plausibility check: a UV photon at 300 nm carries about 4 eV (~6.6 × 10^-19 J), so ~1.5 × 10^18 such photons for 1 J is dimensionally and numerically consistent.