76. An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of ?

75. A astronomical telescope has objective and eyepiece of focal lengths 40 cm and 4 cm respectively. To view an object 200 cm away from the objective, the lenses must be separated by a distance :

74. In an astronomical telescope in normal adjustment a straight black line of length L is drawn on inside part of objective lens. The eyepiece forms a real image of this line. The length of this image is l. The magnification of the telescope is :

73. If the focal length of objective lens is increased then magnifying power of :

72. For a normal eye, the cornea of eye provides a converging power of 40D and the least converging power of the eye lens behind the cornea is 20D. Using this information, the distance between the retina and the eye lens of the eye can be estimated to be ?

71. The magnifying power of a telescope is 9 . When it is adjusted for parallel rays the distance between the objective and eyepiece is 20 cm. The focal length of lenses are :

70. A microscope is focussed on a mark on a piece of paper and then a slab of glass of thickness 3 cm and refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again ?

69. A telescope has an objective lens of 10 cm diameter and is situated at a distance of one kilometer from two objects. The minimum distance between these two objects, which can be resolved by the telescope, when the mean wavelength of light is 5000 Å, is of the order of ?

68. An astronomical telescope has a length of 44 cm and tenfold magnification. The focal length of the objective lens is ?

67. The hypermetropia is a ?