Tipe file yang diizinkan untuk diupload

Sore gan. Saya mau nanya gimana caranya membatasi tipe file/ekstensi yang boleh diupload. Misalkan hanya boleh upload file bertipe .jpg .png, dsb.

ini function simpan/upload data saya:

 public function store(Request $request)
    {
        $file = $request->file('owner_photo');
        $fileName = $file->getClientOriginalName();
        $file->move("uploads/file", $fileName);

        $file2 = $request->file('dealer_photo');
        $fileName2 = $file2->getClientOriginalName();
        $file2->move("uploads/file", $fileName2);

        $credentials = [
            'dealer_name' => $request->dealer_name,
            'username' => $request->username,
            'password' => $request->password,
            'office_address' => $request->office_address,
            'phone_number' => $request->phone_number,
            'owner_photo' => $fileName,
            'dealer_photo' => $fileName2,
        ];

        $user = Sentinel::registerAndActivate($credentials);

        $role = Sentinel::findRoleBySlug('finance');

        $role->users()->attach($user);

        return back()->with('create', 'A new dealer added!');
    }

Berdasarkan code diatas, ekstensi file apapun yang saya upload tetap bisa disimpan. Sedangkan kebutuhan program hanya boleh mengupload file gambar.

Mohon bantuannya. Terima kasih.