Dispersion of white light through a prism occurs because
A. Different colours have same speed in glass
B. White light is composed of seven colours
C. Refractive index is different for different colours
D. Prism absorbs colours
Answer: Option C
Solution (By JKSSB Mock Tests)
Dispersion is splitting of light into constituent colours due to variation of refractive index with wavelength. Violet deviates most, red least. Prism doesn't absorb but disperses. Rainbow formation is due to dispersion, refraction, reflection in water droplets.
Explanation:
The formula for capacitors in series is exactly the opposite of resistors. 1/C_eq = 1/C1 + 1/C2 + 1/C3. Here, all are 3 uF. So, 1/C_eq = 1/3 + 1/3 + 1/3 = 3/3 = 1. Therefore, C_eq = 1 microfarad. When identical capacitors are in series, you simply divide the capacitance by the number of capacitors (3/3 = 1).
Assertion (A): A fuse wire must have a high resistance and a low melting point. Reason (R): This ensures it melts quickly and breaks the circuit when an excessively high current flows.
A.A is true but R is false.
B.Both A and R are true and R is the correct explanation of A.
C.Both A and R are true but R is NOT the correct explanation of A.
Explanation:
A fuse is a safety device. It must have a relatively high resistance so that it produces heat quickly when a large current passes through (H = I²Rt). It must have a low melting point so that this heat causes it to melt immediately, breaking the circuit and protecting appliances. Thus, both A and R are true, and R explains A.
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