The threshold photoelectric effects in tungsten is produced by light of a wavelength 260 nm give the energy of a photon of this light in joules.

Energy of light is

Explanation:

Given:

Wavelength

Also we know the speed of light

To calculate frequency of light , divide speed of light by Wavelength

Hence frequency is

Now, To calculate energy (E), we need to multiply planks's constant with the frequency of light  .

Also Plank's Constant =

Hence Energy of light is

explanation:

metals have excess of electrons whereas non-metals have deficiency of electrons. thus, in order to gain stability metals easily donate their electrons to the non-metals.

for example, electronic configuration of sodium is and electronic configuration of phosphorous is .

when a phosphorous atom and sodium atom combine together then sodium will donate is extra one electron to the phosphorous atom. as a result there will be formation of ionic bond between sodium and phosphorous.

the reaction will be as follows.

there, are three sodium sodium atoms and each of them will donate its one extra electron to phosphorous atom. thus, the sub-shell of phosphorous gets completely filled.  

thus, we can conclude that electrons are transferred from atoms of sodium to atoms of phosphorous. this transfer makes the sodium atoms donate one electron and the phosphorous atoms to gain one electron. as a result, the sodium and phosphorus atoms strongly attract each other.

answers: to make sure that all of the broken pieces of tablet were added to the water, to allow for fair comparison of all three trials, with different particle sizes to avoid experimental error