What happens when monochromatic light travels from one medium to another ? Assertion (A) : its Wavelength changes Reason (R) : its Frequency remains same

R is true, A is false A is true, R is false Both are true R is the correct explanation of A

Both are true

R is NOT the correct explanation of A because it does not say anything about the velocity of the light. Option 3 is sure-shot true as both the statements are true.