what is the frequency in hertz of a photon of light with an energy of 5.94 x 10-21j?

Planck constant, h = 6.626 × 10⁻³⁴ J s
Energy, E = 5.94 × 10⁻²¹ J
Frequency, ν = ? Hz

E = hν
Frequency, ν = E/h = (5.94 × 10⁻²¹ J) / (6.626 × 10⁻³⁴ J s) = 8.96 × 10¹² Hz

Given,

Energy (E) = 5.94 x 10¯²¹J

Planck’s constant (h) = 6.626 x 10¯³⁴J.sec

Frequency (f) = ?

We know that:-

Energy (E) = planck’s constant (h) x frequency (f)

Frequency (f) = Energy (E) / planck’s constant (h)

= 5.94 x 10¯²¹J / 6.626 x 10¯³⁴J.sec

= 0.396 x 10¯²¹⁺³⁴/sec

= 0.896 x 10¹³/sec

≈ 8.96 x 10¹²Hz

∴ frequency (f) = 8.96 x 10¹²Hz.

5.94 x 10-21j ?? what does this mean ? Energy is not a vector.

in any case use this:
Energy equivalent to an EM photon
E = hf, where h = Plank's constant 6.626e-34 Js
E = hc/λ (alternate form)
E is the energy of the particle in Joules
f is frequency in Hertz, λ is wavelength in meters
c is speed of light in m/s, aprox 3e8 m/s