law: 4. Mischief causing damage to public property by fire or explosive substance.-
  Whoever commits an offence under sub-section (1) or sub-section (2) of section 3 by fire or explosive substance shall be punished with regorous imprisonment for a term which shall not be less than one year, but which may extend to ten years and with fine:
  Provided that the court may, for special reasons to be recorded in its judgment, award a sentence of imprisonment for a term of less than one year.