1
JEE Main 2025 (Online) 23rd January Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

Heat treatment of muscular pain involves radiation of wavelength of about 900 nm . Which spectral line of H atom is suitable for this?

Given : Rydberg constant $\left.\mathrm{R}_{\mathrm{H}}=10^5 \mathrm{~cm}^{-1}, \mathrm{~h}=6.6 \times 10^{-34} \mathrm{~J} \mathrm{~s}, \mathrm{c}=3 \times 10^8 \mathrm{~m} / \mathrm{s}\right)$

A
Lyman series, $\infty \rightarrow 1$
B
Balmer series, $\infty \rightarrow 2$
C
Paschen series, $5 \rightarrow 3$
D
Paschen series, $\infty \rightarrow 3$
2
JEE Main 2025 (Online) 22nd January Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

Given below are two statements :

Statement (I) : A spectral line will be observed for a $2 p_x \rightarrow 2 p_y$ transition.

Statement (II) : $2 \mathrm{p}_x$ and $2 \mathrm{p}_y$ are degenerate orbitals.

In the light of the above statements, choose the correct answer from the options given below :

A
Statement I is false but Statement II is true
B
Both Statement I and Statement II are false
C
Statement I is true but Statement II is false
D
Both Statement I and Statement II are true
3
JEE Main 2025 (Online) 22nd January Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

Radius of the first excited state of Helium ion is given as : $\mathrm{a}_0 \rightarrow$ radius of first stationary state of hydrogen atom.

A
$\mathrm{r}=\frac{\mathrm{a}_0}{4}$
B
$\mathrm{r}=2 \mathrm{a}_0$
C
$\mathrm{r}=4 \mathrm{a}_0$
D
$\mathrm{r=\frac{a_0}{2}}$
4
JEE Main 2024 (Online) 9th April Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency '$$A$$' $$\times 10^{12}$$ hertz and that has a radiant intensity in that direction of $$\frac{1}{{ 'B'}}$$, watt per steradian. '$$A$$' and '$$B$$' are respectively

A
450 and 683
B
540 and $$\frac{1}{683}$$
C
540 and 683
D
450 and $$\frac{1}{683}$$
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