MCQ
X-rays of $\lambda=1 \mathrm{~A}^0$ have frequency
  • A
    $3 \times 10^{8} \mathrm{~Hz}$
  • $3 \times 10^{18} \mathrm{~Hz}$
  • C
    $3 \times 10^{10} \mathrm{~Hz}$
  • D
    $3 \times 10^{15} \mathrm{~Hz}$

Answer

Correct option: B.
$3 \times 10^{18} \mathrm{~Hz}$
(b) $3 \times 10^{18} \mathrm{~Hz}$

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$1.$ In the graphs below, the resistance $\mathrm{R}$ of a superconductor is shown as a function of its temperature $\mathrm{T}$ for two different magnetic fields $\mathrm{B}_1$ (solid line) and $\mathrm{B}_2$ (dashed line). If $\mathrm{B}_2$ is larger than $\mathrm{B}_1$ which of the following graphs shows the correct variation of $\mathrm{R}$ with $\mathrm{T}$ in these fields?

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$2.$ A superconductor has $T_C(0)=100 \mathrm{~K}$. When a magnetic field of 7.5 Tesla is applied, its $\mathrm{T}_{\mathrm{c}}$ decreases to $75 \mathrm{~K}$. For this material one can definitely say that when

$(A)$ $\mathrm{B}=5$ Tesla, $\mathrm{T}_{\mathrm{c}}(\mathrm{B})=80 \mathrm{~K}$

$(B)$ $\mathrm{B}=5$ Tesla, $75 \mathrm{~K}<\mathrm{T}_{\mathrm{c}}(\mathrm{B})<100 \mathrm{~K}$

$(C)$ $\mathrm{B}=10 \mathrm{Tesla}, 75 \mathrm{~K}<\mathrm{T}_{\mathrm{c}}<100 \mathrm{~K}$

$(D)$ $\mathrm{B}=10$ Tesla, $\mathrm{T}_{\mathrm{c}}=70 \mathrm{~K}$

Give the answer question $1, 2$