(a) (i) If the lens is placed in water instead of air, how does its fo

1.	(a) (i) If the lens is placed in water instead of air, how does its focal length change? (ii) Which lens, thick or thin has greater focal length? (b) Two waves of the same pitch have amplitudes in the ratio 1 : 3. What will be the ratio of their: (i) intensities and (ii) frequencies? (c) How does an increase in the temperature affect the specific resistance of a : (i) Metal and (ii) Semiconductor? (d) (i) Define resonant vibrations.(ii) Which characteristic of sound, makes it possible to recognize a person by his voice without seeing him ? (e) Is it possible for a hydrogen (11H) nucleus to emit an alpha particle? Give a reason for your
Answer» (a) (i) Its focal length increases. (ii) Thin lens. (b) (i) Ratio of intensities will be 1: 9. (ii) Ratio of frequencies will be 1:1. (c) (i) Increases. (ii) Decreases. (d) (i) If a body is made to vibrate with its fundamental frequency by an external source, then the vibrations are called resonant vibrations. (ii) Quality. (e) No, as it does not possess a helium nucleus.

(a) (i) If the lens is placed in water instead of air, how does its focal length change? (ii) Which lens, thick or thin has greater focal length? (b) Two waves of the same pitch have amplitudes in the ratio 1 : 3. What will be the ratio of their: (i) intensities and (ii) frequencies? (c) How does an increase in the temperature affect the specific resistance of a : (i) Metal and (ii) Semiconductor? (d) (i) Define resonant vibrations.(ii) Which characteristic of sound, makes it possible to recognize a person by his voice without seeing him ? (e) Is it possible for a hydrogen (11H) nucleus to emit an alpha particle? Give a reason for your

Answer»

(a) (i) Its focal length increases.

(ii) Thin lens.

(b) (i) Ratio of intensities will be 1: 9.

(ii) Ratio of frequencies will be 1:1.

(c) (i) Increases.

(ii) Decreases.

(d) (i) If a body is made to vibrate with its fundamental frequency by an external source, then the vibrations are called resonant vibrations.