Which of these descriptions of units is FALSE? For PAR or PPFD the units are mic

Question

Which of these descriptions of units is FALSE?

For PAR or PPFD the units are micromol m-2 s-1 of energy

The partial pressure of a gas like CO2 in air divided by the total pressure of the air is the same as the concentration of the gas in the air. 40 Pa of CO2 / 100 kPa of air = 400 micromol of CO2/ mol air

Fun fact: 8 mm day-1 of evapotranspiration is equivalent to 8 L of water m-2 ground area day-1

If you can work out why, then congratulations you are as nerdy as the professor!

For solar radiation: W m-2 = J m-2 s-1

For PAR or PPFD the units are micromol m-2 s-1 of energy

The partial pressure of a gas like CO2 in air divided by the total pressure of the air is the same as the concentration of the gas in the air. 40 Pa of CO2 / 100 kPa of air = 400 micromol of CO2/ mol air

Fun fact: 8 mm day-1 of evapotranspiration is equivalent to 8 L of water m-2 ground area day-1

If you can work out why, then congratulations you are as nerdy as the professor!

For solar radiation: W m-2 = J m-2 s-1

Explanation / Answer

A) true

B)False

C)true

D)True

Explanation

A) PAR/photosynthetically active radiation is measured as micro mol photons m2 s1

It is same as photosynthetic photon flux density/PPFD

B) mole fraction=xCO2=p*/p where p*=vapour pressure of pure CO2 gas, p=its partial pressure in mixture

Total P=sum of partial pressures of all gases in the mixture

C)The evapotranspiration rate in mm per unit time. It is the amount of water lost from a surface in the units of water depth on the surface.r.

8 mm day-1 of evapotranspiration is equivalent to 8 L of water m-2 ground area day-1

As one hectare area= 10000 m2

1 mm = 0.001 m,

Loss of 1 mm of water= loss of 10 m3 of water / hectare.

1 mm day-1= 10 m3 ha-1 day-1

8 mm day-1 of evapotranspiration =8 0 m3 /10000 m2 day-1=0.008 m3 /m2 day-1=0.008*1000L /m2 day-1=8L m-2 day-1

D) Irradiance= watt /m2=js-1m-2

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