Which of the following liquid is a poor conductor of electricity?

An isotope has an initial activity of 120 Bq. 6 days later its activity is 15 Bq. The half-life is? 

The secondary pigments consist of?

A person standing waist-deep in a swimming pool appears to have short legs because of light?

A tuning fork having a frequency of 312 Hz emits a wave which has a wavelength of 1.10 m. Calculate the velocity of sound