Any person who, when before a recruiting officer for the purpose of being attested in pursuance of Part I of this Act, has knowingly made a false answer to any question contained in the attestation paper and put to him by or by the direction of the recruiting officer shall, if he has since become and remains subject to air-force law, be liable, on conviction by court-martial, to the like imprisonment as on summary conviction of an offence against section nineteen of this Act or to any less punishment provided by this Act.