1
VITEEE 2021
MCQ (Single Correct Answer)
+1
-0

An object is $$8 \mathrm{~cm}$$ high. It is desired to form a real image $$4 \mathrm{~cm}$$ high at $$60 \mathrm{~cm}$$ from the mirror. The type of mirror needed with the focal length is

A
convex mirror with focal length $$f=40 \mathrm{~cm}$$
B
convex mirror with focal length $$f=20 \mathrm{~cm}$$
C
concave mirror with focal length $$f=-40 \mathrm{~cm}$$
D
concave mirror with focal length $$f=-20 \mathrm{~cm}$$
2
VITEEE 2021
MCQ (Single Correct Answer)
+1
-0

When an object is placed $$40 \mathrm{~cm}$$ from a diverging lens, its virtual image is formed $$20 \mathrm{~cm}$$ from the lens. The focal length and power of lens are

A
$$f=-20 \mathrm{~cm}, P=-5 \mathrm{D}$$
B
$$f=-40 \mathrm{~cm}, P=-5 \mathrm{D}$$
C
$$f=-40 \mathrm{~cm}, P=-2.5 \mathrm{D}$$
D
$$f=-20 \mathrm{~cm}, P=-2.5 \mathrm{D}$$
3
VITEEE 2021
MCQ (Single Correct Answer)
+1
-0

Polonium has a half-life of 140 days. If we take $$20 \mathrm{~g}$$ of polonium initially then the amount of it that remains after 280 days is

A
2.5 g
B
5 g
C
10 g
D
15 g
4
VITEEE 2021
MCQ (Single Correct Answer)
+1
-0

According to Bohr model of hydrogen atom, only those orbits are permissible which satisfy the condition

A
$$m v=n h$$
B
$$\frac{m v^2}{r}=n\left(\frac{h}{2 \pi}\right)$$
C
$$m v r=n\left(\frac{h}{2 \pi}\right)$$
D
$$m v r^2=n\left(\frac{h}{2 \pi}\right)$$
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