Given,

Energy (E) = 3.15 x 10⁻¹⁸J

Frequency (f) = ?

Wavelength (λ) = ?

Planck’s constant(h) = 6.626 x 10⁻³⁴ m².kg/sec

We know that:-

Energy (E) = h x f

Frequency (f) = E/h = 3.15 x 10⁻¹⁸J / 6.626 x 10⁻³⁴

= 0.475 x 10¹⁶

= 47.5 x 10¹⁴Hz

∴ frequency (f) = 47.5 x 10¹⁴Hz

Wavelength (λ) = speed of light (c) / f

= 3 x 10⁸ m/sec / 47.5 x 10¹⁴/sec = 0.063 x 10⁻⁶

= 63 x 10⁻⁹m ≈ 63nm

∴ wavelength (λ) = 63nm.

4.754×10^15 Hz or 63 nm.

E=h*nu, you've been given E and h, solve for nu, the frequency.

c=lambda*nu, you've computed nu, so solve for lambda, the wavelength.

Use google's calculator online. You'll do fine.