Which one of the following statements is not correct?

• The longest wavelength of light visible to human eye is about 700 nm

• The shortest wavelength of light visible to human eye is about 400 nm

• The wavelength of gamma rays is longer than that of X-rays

• The ability of a telescope to form separable images of close objects is called its resolving power.

If the image of an object, formed by a concave mirror is virtual, erect and magnified, then the object is placed:

• at the principal focus

• at the centre of curvature

• beyond the centre of curvature

• between the pole of the mirror and the principal focus

When three resistors, each having resistance r, are connected in parallel, their resultant resistance is x. If these three resistances are connected in series, the total resistance will be:

• 3x

• 3rx

• 9x

• 3/x

Statement I and Statement II. You are to examine these two statements carefully and select the answers to these items using the code given below :

Statement I: Diamond is very bright.

Statement II: Diamond has very low refractive index.

• Both the statements are individually true and Statement II is the correct explanation of Statement I.

• Both the statements are individually true but Statement II is not the correct explanation of Statement I

• Statement I is true but Statement II is false

• Statement I is false but Statement II is true

Statement I and Statement II. You are to examine these two statements carefully and select the answers to these items using the code given below :

Statement I: A body weighs less on a hill top than on earth's surface even though its mass remains unchanged.

Statement II: The acceleration due to gravity of the earth decreases with height.

• Both the statements are individually true and Statement II is the correct explanation of Statement I.

• Both the statements are individually true but Statement II is not the correct explanation of Statement I

• Statement I is true but Statement II is false

• Statement I is false but Statement II is true

Ultrasonic waves of frequency 3 x 10⁵ Hz are passed through a medium where speed of sound is 10 times that in air (Speed of sound in air is 300 m/s). The wavelength of this wave in that medium will be of the order of

• 1 cm

• 10 cm

• 100 cm

• 0.1 cm

157.

If radius of the earth were to shrink by 1%, its mass remaining the same, g would decrease by nearly

• 1%

• 2%

• 3%

• 4%

The displacement-time graph cf a particle acted upon by a constant force is

• a straight line

• a circle

• a parabola

• any curve depending upon initial conditions

Which one of the following is not a result bf surface tension?

• Nearly spherical drop of rain

• Capillary rise

• Removal of dirt by soap or detergent

• Flow of a liquid

Which one among the following happens when a swing rises to a certain height from its rest position?

• Its potential energy decreases while kinetic energy increases

• Its kinetic energy decreases while potential energy increases

• Both potential and kinetic energy decrease

• Both potential and kinetic energy increase