A convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together. What will be their resulting power?
+ 6.5 D
- 6.5 D
+7.5 D
-0.75 D
For the given incident ray as shown in figure, the condition of total internal reflection of the ray will be satisfied if the refractive index of block will be
The hypermetropia is a
short-sight defect
long-sight defect
bad vision due to old age
None of the above
2 convex lenses
2 concave lenses
1 convex, 1 concave lens
1 convex and 1 plane mirror
If fv and fn are the focal lengths of a convex lens for violet ad red light respectively and FV and FR are the focal lengths of concave lens for violet and red light respectively, then we have :
fV < fR and FV > FR
fV < fR and FV < FR
fV > fR and FV > FR
fV > fR and FV < FR
A telescope has an objective lens of 10cm diameter and is situated at a distance of one kilometre from two objects. Find out the minimum distance between these two objects, which can be resolved by the telescope, when the mean wavelength of light is 5000 Å.
0.5 m
5 m
5 mm
5 cm
Pick out the longest wavelength from the following types of radiations.
Blue light
Gamma rays
X-rays
Red light
Interference is possible in
light waves only
sound waves only
Both light and sound waves
Neither light nor sound waves
If two mirrors are kept inclined at 60° to each other and a body is placed at the middle, then total number of images formed is :
Six
Five
Four
Three
One face of a rectangular glass plate 6 cm thick is silvered. An object held 8 cm in front of the first face, forms an image 12 cm behind the silvered face. The refractive index of the glass is :
0.4
0.8
1.2
1.6
