Answer:
A. {K}, {Ba}, {Ca}, {Na}
B. {Au}
C. {Na}
D. Image Missing
Explanation:
PART A:
The range of wavelengths in visible region is 380 nm to 740 nm. Thus, all the elements that emit light of wavelength in this region are the elements which emit radiation in visible part. They are:
{k}
{Ba}
{Ca}
{Na}
PART B:
The energy of a photon is inversely proportional to its wavelength (E = hc/λ). Therefore, the element, which emits the radiation of smallest wavelength, has the highest energy photons. That element is {Au}
PART C:
Similarly, the element which emits radiation of highest wavelength, has the lowest energy. That element is {Na}
PART D:
Image missing.