In the reaction given below . How many α and β particles are emitted?
6α, 3β
3α, 4β
4α, 3β
3α,6β
If a convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together, what will be their resultant power?
+0.65 D
-0.65 D
+0.75 D
-0.75 D
The phenomenon of radioactivity is :
exothermic change which increases or decreases with temperature
increases on applied pressure
nuclear process does not depend on external factors
none of the above
C.
nuclear process does not depend on external factors
Radioactivity is a natural process which does not depend upon external factors.
The amplification factor of a triode valve is 15. If the grid voltage is changed by 0.3 V, the change in plate voltage in order to keep the current constant (in volt) is :
0.02
0.002
4.5
5.0
A plane glass slab is kept over various colour letters, the letter which appears least raised is :
red
violet
green
blue
A convex lens forms a full image of the object on a screen. If half of the lens is covered with an opaque object, then :
the image disappears
half of the image is seen
full image is seen and of same intensity
full image is seen and of decreased intensity
The time taken by light to pass through 4 mm thick glass slab of refractive index 1.5 will be : (velocity of light in air= 3 x 108 m/s)
8 × 10-11 s
2 × 10-11 s
8 × 10-8 s
2 × 10-8 s
A lens acts as converging in air and diverging when immersed in water. Then, refractive index of lens is :
equal to unity
below 1.33
greater than 1.33
less than unity
A light passing through air has wavelength 6000 Ao. The wavelength when same ray passes through a glass slab of refractive index 1.5 will be:
2000 Ao
4000 Ao
8000 Ao
1200 Ao