Answer: Violet and Blue color
Step-by-step explanation:
From photoelectric effect, we understand that when a radiation of frequency equal or greater than threshold frequency of metal falls on it, electrons are ejected. Thus, the color which will eject electrons when they strike sodium which has a threshold frequency of 5.7 × 10¹⁴ Hz should have greater frequency than its.
The frequency of Blue color is 6.6× 10¹⁴ Hz and violet is 7.3 × 10¹⁴ Hz . Thus, these two colors would be able to eject electrons from Sodium. Rest of the colors have lower frequency than threshold.