A radioactive sample has half-life of 5 years. The percentage of fraction decayed in 10 years will be

An isotope of the original nucleus can be formed in a radioactive decay, with the emission of following particles.

Two different radioactive elements with half lives '$$\mathrm{T}_1$$' and '$$\mathrm{T}_2$$' have undecayed atoms '$$\mathrm{N}_1$$' and '$$\mathrm{N}_2$$' respectively present at a given instant. The ratio of their activities at that instant is

In Balmer series, wavelength of the $$2^{\text {nd }}$$ line is '$$\lambda_1$$' and for Paschen series, wavelength of the $$1^{\text {st }}$$ line is '$$\lambda_2$$', then the ratio '$$\lambda_1$$' to '$$\lambda_2$$' is