The ratio of magnetic fields due to a bar magnet at the two axial points P₁ and P₂ which are separated from each other by $10 \mathrm{cm}$ is $25:2$. P₁ Point is situated at$10 \mathrm{cm}$ from the centre of the magnet. (Points P₁ and P₂ are on the same side of magnet and distance of P₁ and P₂ from the centre of magnet is much greater than the distance of two ends of the magnet from the centre). Magnetic length of the bar magnet is

• A

  $5 \mathrm{cm}$

   
• Correct answer
  B

  $10 \mathrm{cm}$

   
• C

  $15 \mathrm{cm}$

   
• D

  $20 \mathrm{cm}$

   

Hence, the correct answer is option: 'B'.