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2. structure of atom — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistry2. structure of atom1 Mark
MCQ
The work function $(\phi)$ of some metals is listed below. The number of metals which will show photoelectric effect when light of $300 \ nm$ wavelength falls on the metal is
Metal $Li$ $Na$ $K$ $Mg$ $Cu$ $Ag$ $Fe$ $Pt$ $W$
$\phi( eV )$ $2.4$ $2.3$ $2.2$ $3.7$ $4.8$ $4.3$ $4.7$ $6.3$ $4.75$
  • ✓
    $4$
  • B
    $5$
  • C
    $6$
  • D
    $7$
✓

Answer

Correct option: A.
$4$
a
the enrgy associated with incident photon $\frac{h c}{\lambda}$

$\Rightarrow E=\frac{6.6 \times 10^{-34} \times 3 \times 10^8}{300 \times 10^{-90} J}$

$E \text { in } eV =\frac{6.6 \times 10^{-34} \times .3 \times 10^8}{300 \times 10^{-9} \times 1.6 \times 10^{-19}}=4.16 eV$

So, number fo metal showing phote -electric effects whill be

$(4) , i, e, Li, na, K, Mg, .$

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