1
JEE Main 2018 (Online) 15th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
The energy required to remove the electron from a singly ionized Helium atom is $$2.2$$ times the energies required to remove an electron from Helium atom. The total energy required to ionize the Helium atom completely is :
A
$$20$$ $$eV$$
B
$$34$$ $$eV$$
C
$$79$$ $$eV$$
D
$$109$$ $$eV$$
2
JEE Main 2018 (Online) 15th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A planoconvex lens becomes an optical system of $$28$$ $$cm$$ focal length when its plane surface is silvered and illuminated from left to right as shown in Fig-A.

If the same lens is instead silvered on the curved surface and illuminated from other side as in Fig-B, it acts like an optical system of focal length $$10$$ $$cm.$$ The refractive index of the material of lens is :

JEE Main 2018 (Online) 15th April Morning Slot Physics - Geometrical Optics Question 208 English
A
$$1.50$$
B
$$1.55$$
C
$$1.75$$
D
$$1.51$$
3
JEE Main 2018 (Online) 15th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A Helmholtz coil has a pair of loops, each with $$N$$ turns and radius $$R$$. They are placed coaxially at distance $$R$$ and the same current $${\rm I}$$ flows through the loops in the same direction. $$P,$$ midway between the centers $$A$$ and $$C$$, is given by [Refer to figure given below] :

JEE Main 2018 (Online) 15th April Morning Slot Physics - Magnetic Effect of Current Question 186 English
A
$${{8N{\mu _0}{\rm I}} \over {{5^{1/2}}R}}$$
B
$${{8N{\mu _0}{\rm I}} \over {{5^{3/2}}R}}$$
C
$${{4N{\mu _0}{\rm I}} \over {{5^{1/2}}R}}$$
D
$${{4N{\mu _0}{\rm I}} \over {{5^{3/2}}R}}$$
4
JEE Main 2018 (Online) 15th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
Light of wavelength $$550$$ $$nm$$ falls normally on a slit of width $$22.0 \times {10^{ - 5}}$$ $$cm.$$ The angular position of the second minima from the central maximum will (in radians) :
A
$${\pi \over {12}}$$
B
$${\pi \over 8}$$
C
$${\pi \over 6}$$
D
$${\pi \over 4}$$
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