What percentage of a given mass of a radioactive substance will be left undecayed after five half-life periods?

A metal wire under constant potential difference, when heated, shows that the drift velocity of the electron :

Arrange the following in the increasing order of de-Broglie wavelength:
A. A bullet of mass 0.02 kg travelling at speed of 3.3 km s⁻¹
B. A ball of mass 0.0331 kg moving with speed of 2 m s⁻¹
C. A dust particle of mass \( 2 \times 10^{-10} \text{ kg} \) drifting with a speed of 3.3 m s⁻¹
D. A photon having a momentum of \( 6.63 \times 10^{-26} \text{ kg m s}^{-1} \)
E. An electron accelerated through a potential difference of 100 V
Choose the correct answer from the options given below:

A square loop is placed near a long straight current carrying wire as shown in figure. If the loop is moved away from the wire

The correct formula for range of a transmitting antenna of height '2h' is: (Given R = radius of the Earth)

If focal length of a concave lens is 50 cm, then the power of the lens would be

A piece of copper and a piece of germanium are cooled from room temperature 20 C down to 80 K. The resistance of

A radioactive nucleus M undergoes series of decays given below: M \(\xrightarrow{\beta^- decay}\) N \(\xrightarrow{\gamma decay}\) O \(\xrightarrow{\alpha decay}\) P. The mass number of M is 150 and Atomic No of M is 64. The Atomic number of P is

Arrange the following evolutionary human species in order of their appearance on earth from the current to the oldest one.
(A) Homo erectus
(B) Neanderthal man
(C) Dryopethicus
(D) Homo sapiens
Choose the correct answer from the options given below:

A solution of CuSO _4 is electrolysed for 10 minutes using a current of amperes. ( 1 mol of \(Cu =63 g\) ). How much copper is deposited at cathode
\(1 F=96487 C mol^{-1}\)

Cells responsible for the synthesis and secretion of testicular hormones are:

Read the given passage and answer the following questions:
Secondary treatment or biological treatment: The primary effluent is passed into large tanks where air is pumped into it. This allows vigorous growth of aerobic microbes. While growing, these microbes consume the major part of the organic matter in the effluent. This significantly change the BOD (biochemical oxygen demand) of the effluent. The effluent in then passed into a tank a small part of the sludge is pumped back into the aeration tank to serve as the inoculum. The remaining major part of the sludge is pumped into large tanks called sludge digesters. Here, other kinds of bacteria grow anaerobically in the sludge. The biogas produced can be used source of energy as it is inflammable. The effluent from the secondary treatment plant is generally released into natural water bodies like rivers and streams.
Steps in primary treatment does not include:

The number of all possible matrices of order \(2 \times 3\) with entries \(-1\) or \(1\) is: